Weather Station Hardware > What Weather Station Should I Buy?

PWS for Rachio?

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hi everyone,

Complete newbie here.

I just purchased a Rachio 3 irrigation controller (I have 11 zones). There are a couple of WUnderground stations near me, but their rain counts are off by ~20% so I'd like to set up my own. I am only really interested in using it as it relates to ET, to allow Rachio to adjust watering times appropriately.

Thinking of spending ~$200 if I can get something ok for that amount? Found this on Amazon:

Would I get a lot more by stretching to $300?



I've been using Rachio for 5 years with my weather station (Davis VP2). Automated rain measurements are not as accurate as a manual gauge, especially during heavy rain. With heavy rain, my rain gauge can be up to 15% lower than my manual gauge - that's a fact for most weather stations because the mechanism (tipping bucket or tipping spoon) can't keep up with the rainfall rate. That said, Rachio will also "decide" whether to water based on the forecast, which can be a problem, especially in the summer due to the more scattered nature of showers and thunderstorms. If the forecast calls for a relatively high chance of rain in the form of showers and thunderstorms, Rachio will not water your lawn in anticipation of the rain. More often than not, it will not rain at my house with those hit and miss storms and I will have to water manually anyway. In the end, having an automated rain gauge in your own yard to trigger your Rachio is a good idea, but it's not foolproof.

I'll take the opposing view of Weatherdoc.

I've had my Rachio for about 5 years as well and love it. I have my Rachio use only my weather station (Davis VP2). My VP2 does an excellent job of measuring rainfall whether it's just a drizzle or a downpour. I have Cocorahs gauge right next to it so I'm able to compare the totals on a regular basis. And they are always extremely close, if not right on. I don't recall Rachio skipping watering very often due to missed rain forecasts. In fact, I don't think I've had to water manually more than a half dozen times since I've had the Rachio.

I'm a big fan of the Rachio. I've sold several neighbors on getting one. In fact, they just point to my weather station for their Rachio to use.


I don't have Rachio but do have the Hydrawise/Hunter system controller and have selected my WU station as well as some other local WU contributors in the Weather Station settings.  As Steve mentioned the Davis VP2 is very close and mostly identical to my manual CoCoRaHS but I have less confidence in WU or its forecast as it relates directly to my location so I have added the Hunter RainClick sensor to the controller.  The rain sensor makes sure the irrigation is stopped when it actually rains, and doesn't restart until the sensor is actually dry (very important for our extremely high water/sewer-surcharge rates).


My CoCoRaHS is next to my Davis as well. I agree with SteveFitz1 that most of the time the Daivs and CoCoRaHS measurements are very close - typically within 0.01" - except for high rainfall rates. Thunderstorm type rain rates are typically about 15% low with the Davis. I found the same to be true with my first Davis that I had in Florida for 8 years. I kept detailed records of Davis versus CoCoRaHs for about 6 years and with rainfall rates about 1" per hour or more, the tipping bucket couldn't keep up.

As far as missed rain forecasts, I should qualify the issue where I live. In northern Virginia, I live about 5 miles east of the Bull Run Mountains at the eastern edge of the Blue Ridge Mountains, which are 20 miles west of my house. The Bull Run Mountains are about 700 ft in elevation and the Blue Ridge about 2000 ft. That's just enough to cause thunderstorms moving eastward across the mountains to dissipate in my vicinity due to downslope and drying and often to reform about 5-10 miles east of my house. Yet the Rachio will not water because the forecast is for thunderstorms, but the forecast is not fine scale enough to recognize the microclimate just east of the mountains.

I do rely on my Rachio and I would recommend having your own weather station to support it. Many of my neighbors rely on my Davis for their Rachio.

I do have a question for redcoat: how do you know a couple of Wunderground stations near you are off by ~20%?


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