Topic: Marked temperature variations over relatively short distances

[DaleReid]

This morning while looking at my weather observations recorded by a couple stations and comparing to surrounding locations I noticed something weird, or what I thought was.

Some of the Univ of Utah MesoWest network stations are amateur, like mine.  Some are official as can be found, such as Dept of Natural Resources stations or AWOS and other observations from government sponsored and maintained equipment (which in my mind should reflect pretty accurate readings).

None are, as far as I'm aware, a loose cannon wanting to have the lowest or highest readings for temperatures or rain or wind or snowfall.

Many of us here have high quality amateur stations like Davis, etc. Most of those auto report to CWOP and don't depend upon user entry of the values.

My stations are amateur, but four of them use (and agree within a part of a degree or so of one another) research/government/aviation quality sensors such as RM Young, Campbell Scientific, Vaisala and so on.

Here's what caught my attention this morning. I'm about 5 miles southwest of a moderate sized city and my temp was currently about zero.  The seven or eight stations just north of me (including a full ILS commercial airport) were -11 to -14.  A DNR Ranger station about 15 miles  to my east was about -10.  An airport and a few other stations 25 miles to the southeast was -8 or so.

Certainly during times of  no wind and very cold temperatures and clear skies I've seen 'pockets' of noticably colder temps be reported.  I had heard them described as cold air 'draining' down into valleys etc., although I'm not sure how that might work.

As the temps warmed  up this morning my stations all came  up together again following within a degree or so of each other. I got my long woolies on and checked a few Taylor mercury thermometers and they were in agreement with my automated stations, and comparing to the surrounding stations in the area and the airport, the readings were pretty well in agreement.

So what gives with 'pockets' of warmer or colder temps, enough to stand out when looking at the surrounding area readings (other than precip reports and all) are usually in good agreement?

I'm looking for  some science if there is any.

Oh, one thing I do recall.  Thirty years ago we had gotten a new Dodge Caravan which, for the time, was new to me to have a digital thermometer in the panel.  We had driven down to my parent's place in central Wisconsin for Christmas eve and after we headed back and the kids were asleep, I amused myself by not old watching out for deer by watching the outdoor readings.  It was brutally cold, -20s, and I noticed something that I'd not admit to earlier, which was that in the lower valley areas the temps were indeed several degrees colder and when we climbed onto ridges and traveled for a few miles the temps were higher.  This was repeatable and a chance to see weather observations in action with my new toy of an outside temp gauge, which was moving.

Can colder air 'drain' into lower areas?

Dale

[R.Sidetrack]

Can colder air 'drain' into lower areas?

Here is a 1975 Field Study with numbers:
Cold air drainage: a field experiment - UWM Digital Commons

[DaleReid]

I had no idea such measurements were done and a nice paper published to distribute the findings.

I am not sure  how you found the paper, but it was exactly what I was looking for.

Thank you. Dale

[R.Sidetrack]

I am not sure  how you found the paper, but it was exactly what I was looking for.

Actually, I used a 'quote' from your initial post as a Google search phrase. Here is what I gave  Google: "Can colder air 'drain' into lower areas?"

Here is another interesting result from that same query: https://www.canr.msu.edu/news/analyzing_and_improving_your_farms_air_drainage

[DaleReid]

The article on figuring  out how to get air to flow seems odd at first, but makes good sense after reading it.

We have a lot of apple orchards here, and while on hilly areas, there are a couple which have set  up big fans (think miniature are wind generators) about 50' tall and move air a bit which may be enough to prevent frost damage.

One think I just recalled.  For a few years I was in a 4 story building on a steep bank next to the Chippewa River.  In addition to watching for eagles, it was a nice place to have a perch to watch weather while sitting at  my desk.

One very unusual thing I saw and wish that smartphone cameras or web cams were available back then, was looking up the river just before dusk one late late fall afternoon when the water wasn't frozen over yet.  In very slow motion a completely obscuring fog bank slowly rolled down the river contained by relatively steep banks.  This wasn't reflected along side the river on higher ground with any fog formation.  It was if a slow progressive wave of say whipped cream came along the surface.  It took perhaps 15 minutes to migrate slowly down a 1/2 mile or so. 

The conditions must have been perfect, with little or no wind, near 100% humidity and cloudy conditions favoring fog formation, and something must have triggered it.  Extremely fascinating and never saw such a thing again.  I'm thinking that microclimate changes are more prevalent but just not easily visible.

I'm used to seeing smoke or dust be moved by wind. Air certainly can be moved by its change in density and weight on it's own part.

[hofpwx]

Definitely yes. From our place south along a bike path is an elevation drop of only about 50 feet into a creek drainage but the temperature difference can be palpable - several degrees F.

Also, we get descending westerlies ("chinooks") that push the cold air east (downslope), but if the winds stop, that cold air can come sloshing back. The swings can be dramatic. I'll see if I can dig up an example.

[CW7491]

If you like extreme examples like I do, check out Peter Sinks, UT.
https://climate.usu.edu/PeterSinks/

Here is a screen shot of 20 Jan 2025 at 9a local time showing the temperature on the rim and down in the sink.
 
 [ You are not allowed to view attachments ]

I think the best east coast example is Canaan Valley NWR, WV. Like Utah State, VA Tech has set up weather equipment there. Here is a screenshot of 23 Jan 2025 at 7a local time.

 [ You are not allowed to view attachments ]

I’m not certain, but I think for both of these examples the two stations are less than 1 mile apart.

[Central Maine Weather]

This microclimate phenomenon happens to me all the time. The nearest NWS official reporting station is our state capital airport in Augusta, Maine. It is located up on a small hill in the open and regularly reports temps 10-15F higher than all surrounding areas.

For example, currently the temp being reported at the airport is 11F above zero, meanwhile the temp on my two Davis Vantage Pro2 stations in Manchester, ME just a couple miles west of the airport show -3F! My two Davis stations are a quarter mile apart from each other but are both ~2 miles from the airport station. I’m located in a chilly valley, but the airport has always been warm biased in comparison to the rest of the surrounding area because of its location. In fact, 4 different weather stations 2-3 miles east of the airport station are currently showing temperatures between-10F and -14F! That’s a 20+ degree difference just within a few miles!

It’s a daily occurrence here. Sadly the NWS and forecasters in this area use the warm biased readings from the airport when they put out their forecasts, so they are always way off! Something we have to keep in mind in the agricultural industry when keeping an eye on frost risk during the shoulder seasons. We always know to safely knock ~10F off of the forecasted low temperatures each night for our area in order to better represent what the low temperatures will ACTUALLY be for us.

They’ve gone so far as even changing our hardiness zone because of years of warm biased climate data from said airport weather station over the past decades.


The microclimate effect is really amazing, it’s just too bad an entity as big as the NWS doesn’t catch on to the fact that some of their ASOS reporting stations are in poor locations that are misrepresenting the majority of the surrounding area (in my case they are a warm biased location).

[DaleReid]

The knowledge, experience and sharing spirit here is amazing.
I have learned so much from this discussion.
Thanks. 
(PS not all is computer modeling!)

[zackdog]

Funny that I found this today. I live on the side of a mountain in the Fraser Valley in Colorado.  Ever since I discovered that CDOT had weather stations with some of their traffic cameras, I have been checking the one in Tabernash.  Tabernash is basically the low point in the valley.  It was reading -17°F while my Davis VP2 was only reading 5°F. I am located 3.3 miles away, but am 380 feet higher.

My VP2 is about 11 years old so I was worried that my temperature sensor might need replacement.  I have a separate temperature sensor that monitors different rooms or the garage. This morning I took it out and placed it next to the VP2.  When it finally bottomed out, it and the VP2 agreed so I guess I won't replace the sensor in the VP2.

Overnight on the 21st  the CDOT station register a low of -44°F while my low was - 26.5°F. Pretty big difference in 3.3 miles and 380 feet difference in elevation. Both last night and the 21st were clear calm nights.

Mark

[hofpwx]

They’ve gone so far as even changing our hardiness zone because of years of warm biased climate data from said airport weather station over the past decades.

Just one station isn't enough to change a hardiness zone.

The microclimate effect is really amazing, it’s just too bad an entity as big as the NWS doesn’t catch on to the fact that some of their ASOS reporting stations are in poor locations that are misrepresenting the majority of the surrounding area (in my case they are a warm biased location).

NWS is well aware of microclimates. Anomalies from a long-term baseline are often more useful for analysis.

[RIKIAWS]

What a great discussion!!

[Central Maine Weather]

Just one station isn't enough to change a hardiness zone.


NWS is well aware of microclimates. Anomalies from a long-term baseline are often more useful for analysis.

Correct, but when you live in an area that only has a couple ASOS stations in the entire state, and one of those very few provides warm biased data, it skews the long term climate anomalies for the area. You’d have to see/experience what I’m talking about in order to understand.
I’m also well aware that NWS knows about microclimates. What I said was it’s too bad when they submit their forecasts that those forecasts reflect the warm biased readings from said ASOS station, instead of reflecting what will happen as a better representation for the entire area as a whole.
I’m by no means bashing the NWS here, so please don’t take it that way. I’m just stating the fact that forecasts rely too heavily nowadays on computer models and what data is ingested by those computer models. If that data is inaccurate for representing a general area, the forecast spit out by computers will be off. There just doesn’t seem to be as much physical forecasting as there used to be based off of experience and “gut” instinct. What has history told us about a particular storm setup so to speak. Way more reliance on what does the computer tell me is going to happen.
I know it’s not a perfect science and that’s what we all love so much about it! Keeps us on our toes!

[Central Maine Weather]

See attachment for the current forecast wind chill temperatures (in this example) for tonight put out by our local NWS office in southern Maine. Notice Augusta, Maine (the suspect warm biased ASOS site I’ve been talking about) with a forecast of -8F. Meanwhile coastal locations to our south which truly in real life are warmer sites, are forecasted the same or even colder temperatures than Augusta is, even though Augusta is one of the windier ASOS sites in the state and therefore should see lower wind chill readings on this map. This higher forecasted temp for Augusta is only due to the fact that their forecasted actual temperature is much higher than other locations. When I do a point forecast for Augusta, it shows a low forecast air temperature tonight of -2F. Point forecast temps around the area outside of this warm biased zone are in the -10 to -15F range. There will not actually be this dramatic of a difference that happens even though this is what is always shown on forecasts for this area.

Also notice the color coding on the map (the dark purple indicating “warmer” readings) reaching well inland through Augusta and surrounding areas. Meanwhile to the south in extreme southern Maine there’s a stripe of lighter colors indicating sharply colder readings than what is forecasted in Augusta and surrounding areas well inland right to the coast where they are actually influenced by the warmer ocean typically keeping them a bit warmer. Yet the forecast never reflects this.

Now compare this forecast map for tonight with the Hardiness Zone map and see the correlation. Notice how hardiness zone 5b surges north through Kennebec county. I’m confident this is because of the warm biased readings they get from the Augusta ASOS station which biases the entire surrounding area. This is why I’m saying it’s a poor misrepresentation of the surrounding areas well inland.

I live just west of Augusta and know others with PWS’s (good high quality ones like Davis or Rainwise sites in ideal locations) all around the area and they all read significantly colder (especially overnight) compared to Augusta as I stated in my original post. We cannot grow plants that are zone 5 hardy here. They will eventually die from winter cold. According to this hardiness map our Average Annual extreme minimum temperature here should be between -10F and -15F. We’ve hit -15F 3 times this winter already (not including wind chill). Last winter we bottomed out at -20F a few times and the winter before -25F. Zone 5 hardy plants die in those temps.

I just wanted to provide this info as an example of extremes and microclimate effects. In my case and through years of being a vigilant observer, I can confidently say the warm biased readings from Augusta Maine’s ASOS station is skewing forecast temps and climate temps for the surrounding area.

Again I’m not complaining, just making observations that I feel are shareable here. 
I have actually reached out to our local NWS office and mentioned my thoughts about the matter and they actually agreed with me that Augusta shows higher temperature readings than surrounding areas because of it’s geography (which I’m knowledgeable about), but they said it’s their trusted ASOS station for this region so it is what they have to use with years and years of data behind it. And they don’t seem to notice how dramatically different the actual readings are for this area compared to the Augusta data. I wouldn’t fret if it was a matter of a couple degrees but this is typically on the realm of 5-10 and even upwards of 15+ degree differences at times.

Last week one evening the temp at Augusta’s ASOS station showed +20F
My 2 Davis stations 3 miles west of Augusta at the same time showed -3F
Three other stations (one 2 miles north, one 4 miles east, and one 5 miles south of Augusta) showed -11F, -13F, and -12F respectively. That’s a difference from Augusta of about 30F degrees just within a few miles! And this happens regularly here.

But this is why I love weather! It truly is amazing to see! Keeps us on our toes for sure! 

[ocala]

My work truck from a couple years ago had a temp gauge and I used to see the same anomalies. I work out of Ocala but I drive to Gainesville each day. Going up I-75 you pass through Paynes Praire. It's huge swamp. Roughly 22000 acres. entering the swamp from the south it was 30 degrees. as you past through it it would rise to 36 then back to 30 on the north side. All because the water in the swamp was warmer then the air. Water has a large effect on temperature and the associated wind direction can affect that.
At my house I live in a valley. Well, as much as you can get in Florida. Anyways my temps are consistently lower then the stations around me during the winter. Also on those cold windless nights you can watch the temperature plummet, but a little breeze picks up, no more then 3 or 4 mph and the temp will rise. After the wind dies down the temp drops again.
I love seeing weather data in graphs. Approaching hurricanes, frontal passages etc.   

[DaleReid]

Ocala:
I like your observation about a 'valley in Florida.  And most of the time, semi trucks don't need to chain up to go through mountainous passes in the winter.  All depends on where you are.

I was reminded by your comment of a few years ago when we, who live not too far away but recognize Wisconsin Dells for the tourist trap it is and avoid it at all costs, did take the family for a 'duck' ride, the old World War 2 amphibious vehicles that have been refitted to be scenic carriers (and sort of fun).  As we went along the hour or so tour, we did pass through a shaded area that was also a gully filled with millions of northern ferns.  The strikingly cooler air was so noticeable that several people commented as we passed throguh.

I'm not sure if it was only the shade (there were other shady stretches of road) or the evaporation from the ferns and the somewhat wetter area (both were things that also found along the tour) but it was something the driver/docent commented on being relatively unique to that fern gully that we passed through. 

If you are ever in Wisconsin and near The Dells, take one of the Duck tours. There  is also a jet boat thrill ride which is a thrill, but not all the impressive scenery you'll see on the tour.

From a kid on, living in the north end of the county where the Dells is, and along the bottom of old Glacial Lake Wiscosnin which was enormous, I have been fascinated by the geology of that area.  From more than one source I have read that when a remaining chunk of glacier that was plugging up the outlet of the lake finally let go, most of the water drained out in three to seven days, carving the unique structures of rock that are the present day  Dells. A few chunks of the rock are large as locomotives are found a mile or more down stream.  Quite the gusher.

[hofpwx]

I see the NWS has a couple USCRN stations in Maine. Those will help assess climate normals and correct ASOS biases.

[Central Maine Weather]

I see the NWS has a couple USCRN stations in Maine. Those will help assess climate normals and correct ASOS biases.

Anything helps, but sadly those are nowhere near our location here in South/Central Maine (that I can see anyways).

[CW7491]

See attachment for the current forecast wind chill temperatures (in this example) for tonight put out by our local NWS office in southern Maine. Notice Augusta, Maine (the suspect warm biased ASOS site I’ve been talking about) with a forecast of -8F. Meanwhile coastal locations to our south which truly in real life are warmer sites, are forecasted the same or even colder temperatures than Augusta is, even though Augusta is one of the windier ASOS sites in the state and therefore should see lower wind chill readings on this map. This higher forecasted temp for Augusta is only due to the fact that their forecasted actual temperature is much higher than other locations. When I do a point forecast for Augusta, it shows a low forecast air temperature tonight of -2F. Point forecast temps around the area outside of this warm biased zone are in the -10 to -15F range. There will not actually be this dramatic of a difference that happens even though this is what is always shown on forecasts for this area.

Also notice the color coding on the map (the dark purple indicating “warmer” readings) reaching well inland through Augusta and surrounding areas. Meanwhile to the south in extreme southern Maine there’s a stripe of lighter colors indicating sharply colder readings than what is forecasted in Augusta and surrounding areas well inland right to the coast where they are actually influenced by the warmer ocean typically keeping them a bit warmer. Yet the forecast never reflects this.

Now compare this forecast map for tonight with the Hardiness Zone map and see the correlation. Notice how hardiness zone 5b surges north through Kennebec county. I’m confident this is because of the warm biased readings they get from the Augusta ASOS station which biases the entire surrounding area. This is why I’m saying it’s a poor misrepresentation of the surrounding areas well inland.

I live just west of Augusta and know others with PWS’s (good high quality ones like Davis or Rainwise sites in ideal locations) all around the area and they all read significantly colder (especially overnight) compared to Augusta as I stated in my original post. We cannot grow plants that are zone 5 hardy here. They will eventually die from winter cold. According to this hardiness map our Average Annual extreme minimum temperature here should be between -10F and -15F. We’ve hit -15F 3 times this winter already (not including wind chill). Last winter we bottomed out at -20F a few times and the winter before -25F. Zone 5 hardy plants die in those temps.

I just wanted to provide this info as an example of extremes and microclimate effects. In my case and through years of being a vigilant observer, I can confidently say the warm biased readings from Augusta Maine’s ASOS station is skewing forecast temps and climate temps for the surrounding area.

Again I’m not complaining, just making observations that I feel are shareable here. 
I have actually reached out to our local NWS office and mentioned my thoughts about the matter and they actually agreed with me that Augusta shows higher temperature readings than surrounding areas because of it’s geography (which I’m knowledgeable about), but they said it’s their trusted ASOS station for this region so it is what they have to use with years and years of data behind it. And they don’t seem to notice how dramatically different the actual readings are for this area compared to the Augusta data. I wouldn’t fret if it was a matter of a couple degrees but this is typically on the realm of 5-10 and even upwards of 15+ degree differences at times.

Last week one evening the temp at Augusta’s ASOS station showed +20F
My 2 Davis stations 3 miles west of Augusta at the same time showed -3F
Three other stations (one 2 miles north, one 4 miles east, and one 5 miles south of Augusta) showed -11F, -13F, and -12F respectively. That’s a difference from Augusta of about 30F degrees just within a few miles! And this happens regularly here.

But this is why I love weather! It truly is amazing to see! Keeps us on our toes for sure! 

I certainly understand your frustration and it is a bit surprising that given the proliferation of weather stations, programs like CWOP and good old fashioned local knowledge that some of their point forecasts aren’t more accurate. But I have to say, having lived in Maine years ago and having spent a lot of time in New England, I kind of envy, as a weather enthusiast, the kind of unknown. Most of us live in places that pretty much confirm the known. It’s pretty cool that in 2025 in the eastern US the utility of your weather station is significant for knowing true local conditions. I’d have to imagine aside from remote locations and mountainous regions particularly out west, it’s pretty rare.

[Central Maine Weather]

I certainly understand your frustration and it is a bit surprising that given the proliferation of weather stations, programs like CWOP and good old fashioned local knowledge that some of their point forecasts aren’t more accurate. But I have to say, having lived in Maine years ago and having spent a lot of time in New England, I kind of envy, as a weather enthusiast, the kind of unknown. Most of us live in places that pretty much confirm the known. It’s pretty cool that in 2025 in the eastern US the utility of your weather station is significant for knowing true local conditions. I’d have to imagine aside from remote locations and mountainous regions particularly out west, it’s pretty rare.

I couldn’t agree with you more! It is true, there is some definite excitement that comes from getting a “baseline” forecast from local forecasters and then making our own personal observations and keeping our own personal records based off of what actually happens at any given location. It keeps things even more interesting than they already are. I definitely consider myself lucky to get to experience the things I do here!

[Central Maine Weather]

One last comparison of actual temperatures early this morning in my area for comparison of what I'm talking about/what we see here on a regular basis.

The attached image below is a screenshot from the MESOWEST website showing current temperatures (at the time I took the screenshot) from both CWOP stations and ASOS stations. I have inserted two arrows onto the image. The RED arrow points at the Augusta, ME ASOS station that I've been referring to in this thread that has the significant warm bias in my opinion. The green arrow points at my Davis Vantage Pro2 weather station just a few miles west of Augusta.

As you can see, my station was reporting a temperature of -13F while at the same time the Augusta ASOS station was reporting a temperature of -4F. The more important thing to note is all of the temperatures showing up from other stations around the area. They range from -9F to -17F, with most falling in the -11F to -14F range. Interestingly the -9F you see on the map is the next warmest reading besides the Augusta station, and that -9F is actually the reading from the next closest ASOS station in Waterville, ME, at the small Waterville airport.

As I've mentioned before, these temperature differences are what we see here at least 75% of the time, mainly overnight. The daytime differences aren't as dramatic, but still do exist some of the time. The low temps that actually happen in the entire surrounding area are much lower than what the Augusta ASOS station reports. Keep in mind (see one of my last posts) that the point specific forecast low temperature for us here in Manchester, ME last night was -2F, same as the forecast for Augusta, and we ended up bottoming out at -15.4F while Augusta bottomed out at -6F! Quite the difference from what they were saying for my area but relatively close for the forecast vs. actual for Augusta, and this is a very regular occurrence in this area. I've closely observed other parts of the state for forecasted vs actual temps and they are usually much closer. For some reason the Augusta station and surrounding localities are always way off forecast vs. actual. I truly do attest this to the fact that the NWS and big weather forecasting companies recognize the Augusta ASOS as their "dependable" historical data providing station, whether the data that the station spits out is accurate for the surrounding area as a whole or not. I'm not saying it provides inaccurate data. I'm just saying it mis-represents the rest of the area because of it's geographical positioning on top of a hill where nighttime radiational cooling is non-existent when compared to the whole surrounding area.

Again, just observations I've been making over the years. Definitely and interesting phenomenon! I love to see it, I just wish the NWS and other forecasters would notice how dramatic it is as well and make efforts to provide more accurate forecasts for us in the area for nighttime low temps specifically. It's a very important thing for someone like me who works in agriculture and depends on frost forecasts both at the beginning of the growing season and at the end.

At least we know to expect that actual low temperatures will end up being on average 8-10F lower than what forecasts tell us each night there is efficient radiational cooling. We know during the shoulder seasons that if the forecast shows a low of 42F of lower, we need to expect a frost, because 95% of the time the low temp ends up being in the low to mid 30's in that case.

[Central Maine Weather]

Currently (see attached photo)…
Augusta is showing 12F above zero
My station is at -2F while all others in this large area are between -2F and +4F. Yet again, notice how high the Augusta station is compared to every other station on the map. There’s a theme here that’s been this way for years!
That +9F reading next to the official Augusta station must be another sensor in that vacinity or something because they’re pretty much right on top of each other.

I’m always amazed at this marked temperature difference with the Augusta ASOS always being the significantly warmer station compared to everywhere else around. Very crazy to see!

[RetNavyWeatherLDO]

For example, currently the temp being reported at the airport is 11F above zero, meanwhile the temp on my two Davis Vantage Pro2 stations in Manchester, ME just a couple miles west of the airport show -3F! My two Davis stations are a quarter mile apart from each other but are both ~2 miles from the airport station. I’m located in a chilly valley, but the airport has always been warm biased in comparison to the rest of the surrounding area because of its location. In fact, 4 different weather stations 2-3 miles east of the airport station are currently showing temperatures between-10F and -14F! That’s a 20+ degree difference just within a few miles!

It’s a daily occurrence here. Sadly the NWS and forecasters in this area use the warm biased readings from the airport when they put out their forecasts, so they are always way off!

The microclimate effect is really amazing, it’s just too bad an entity as big as the NWS doesn’t catch on to the fact that some of their ASOS reporting stations are in poor locations that are misrepresenting the majority of the surrounding area (in my case they are a warm biased location).

I used to be an observer, and a forecaster at KNHZ (NAS Brunswick) back in the 70's .. well before the mesonetworks you have now. AUG is at 352 feet on a plateu.  We would AUG as a divert, because often they wouldn't be fogged in ,,

I took a quick look at the Wunderground Map 2/6/25 and the METAR for AUG ... AUG was M13C (9F) and the stations around it are all within 2-3 degrees -- that certainly falls within the realm of local effects, especially in the winter when most of your lakes are frozen ?  .. and snow cover on the ground .  The outlier was Monmouth at 8F.

As you know, the NWS forecasts cover a larger area so I can see where that difference comes in ..  I think they try to average it out for the most part. 

I'm amazed at how much data we get now to feed into the models.  My PWS sensors are at 18 feet right now, down in a small valley - I'm consistently 1 degree cooler than the guys up the hill from me ..

I sure do miss it up there .. we had a camp in Sabattus right on the pond

[Central Maine Weather]

I took a quick look at the Wunderground Map 2/6/25 and the METAR for AUG ... AUG was M13C (9F) and the stations around it are all within 2-3 degrees -- that certainly falls within the realm of local effects, especially in the winter when most of your lakes are frozen ?  .. and snow cover on the ground .  The outlier was Monmouth at 8F.

It's usually nighttime temps that are the issue when comparing the Augusta Station to surrounding areas when radiational cooling is most effective. Typically the AUG station matches much better during the day, or during nights when the effects of radiational cooling aren't as strong due to factors such as wind, cloud cover, active precipitation, etc.

I know based off of this that the AUG station is likely calibrated correctly, the part for me that is challenging is the fact that forecasts are made for this entire area based off of the AUG conditions and historical trends. Because it is a site that doesn't experience significant radiational cooling most nights, forecasts for this area show low temps that are much higher than what actually happens on a very regular basis. Yet another example was last night. Here are the stats...

Forecast low temp for my location in Manchester, ME was 0F
Actual low temp at my location was -9.1F

Forecast low temp for AUG was 0F
Actual low temp at AUG was -2F

As you can see, AUG's forecast vs actual was very accurate, but the forecast vs actual for my location was off by 9F. Not an issue when we're talking about he difference between 0F and -9F, but when we're talking about frost risk with low temps in the 30's vs 40's, that's when it becomes challenging in an industry that relies so heavily on frost forecasting such as agriculture like I'm in. Thankfully we know to keep an eye out for this, and we "make our own forecasts" so to speak by just expecting low temps on ideal radiational cooling nights to be around 6-8 degrees colder than what our point forecast shows. 

I'm hoping in the future forecasts that are computer generated such as the NWS Point forecast will become better at picking up the fact that even though on the map AUG and my site is only 3-4 miles apart as the crow flies, geographical differences have a huge effect on actual weather conditions, especially on active radiational cooling nights that we see so often here in Central Maine (as I'm sure you remember well  ).

I'd love to see the point forecast for my location regularly show forecasted low temps of at least 5-6 degrees colder than the point forecast that's generate for AUG shows, because that's what always happens. We are always AT LEAST 5-6 degrees colder than AUG if not 8-10 degrees being more common. As seen in my past posts on this thread, I can pick pretty much any night I want and you'll see this difference. And it happens with all surrounding towns around AUG, AUG always being the single warm outlier again like you said because of the fact that it sits in the wide open up on top of a plateau.

I sure do miss it up there .. we had a camp in Sabattus right on the pond

It sure is a beautiful area! I always consider myself lucky to live here  And thanks for your input on the matter! I always love hearing knowledge and experience especially from someone who knows this area well and likely knows exactly what I'm talking about with my observations.

[Central Maine Weather]

Last time I’ll post a comparison here, but take a look at this morning… This is a screenshot I just took 5 minutes ago. Everywhere around is in the single digits. Augusta ASOS is showing +19F currently! That’s some 10-15 degrees warmer than any other place around!

Again, this is why it “bothers” me that forecasts are generated (and yes zone hardiness is mainly considered) based off of this one station the state recognizes as the only “official” weather station in this area.

Oh well, guess locals are just going to have to live with the warm biased narrative for this entire area. No one can tell me it’s not happening here, I’m seeing it with my own eyes! If they really cared about accurate data for an entire region they would install sensors elsewhere to get a better representation, but I guess this one warm biased station is good enough for the NWS climatologists in this area. And again I’m not picking on them directly, I just know that if I was after accurate long term data for forecasting and climate use for a specific area I’d desperately want the most accurately representative data I could possibly get.