Thanks Valentine, that pretty much got it! Right, they only let you get 365 days at most, so I had to do it 5 times to get five years. And hope none was a leap year, lol (j/k). But hey, that's close enough.
Bushman, it's a long story and I oversimplified. Hoping not to have to say all this plus create a major distraction that meant my question didn't get answered.
Just remember, you did ask
I live in Atlanta GA USA. It can get below freezing in winter, but rarely goes far below.
Our very modest little old (1978) house has the wonky construction that the main (mid split) level is on a concrete slab, and this slab is exposed to open air at the back of the house.
Meanwhile, the kitchen sink is against the back wall (so there's a window over the sink) and - sigh - the pipes go straight down into the concrete slab, then angle away from the wall (diagonally under the floor, in the slab). I didn't know it when we bought the house but this is unbelievably inefficient, because you essentially have to heat the whole slab of the kitchen floor to get hot water at that sink. And if you stop for a minute, you've lost all your heat headway. It is the opposite of insulation, lol.
Anyway, right at the point where the water pipes go into the slab, before they angle away (an inch from the exposed back of the house), they are liable to freeze if it gets REAL cold outside. (Of course, the slab itself is being heated by the house, which we keep at 68 in winter.) By experience, we have found that the hot water pipe freezes when it gets to the low teens.
It is my tendency to shut off my PC and go stream NetFlix or something on the big screen for a couple hours, before going to bed around midnight. When I go to bed, I pass by our thermostat, which includes an outside sensor so I can see how cold it is outside just before sleepily slouching off to bed in total crash mode.
To finally get to the point, I would like to know which temperatures (at midnight) mean it will probably get in the low teens by dawn. Then I can know to leave the tap dripping, simple as that, without having to start the whole 3-5 minute process of starting my PC again, etc etc, to get all the way to a forecast site.
Said another way: There really should be a very simple relation between the temp at midnight, and the chance it will get to 13 by dawn.
But it is pretty rare. It only happens a few times a winter.
That is why I need many years of data...
What I want to do is find the mornings it got to 13 (or below). First I will use it to set a boundary condition, as in "it never got down to 13 if the midnight temp was at least 24" (or whatever). So then I can discard everything above 24 at midnight (plus know I never have to worry if it's 24).
Then, with what's left, I can plot a "distribution function" (notice my handle is DistFunc) something like this:
If the temp is
23 at midnight, there's a
5% chance it will get to 13 at dawn
If the temp is
20 at midnight, there's a
50% chance it will get to 13 at dawn
If the temp is
16 at midnight, there's a
95% chance it will get to 13 at dawn
Something like that.
So I will have made myself a "rule of thumb" that, somewhere between 16 to 23, I need to start the the tap dripping.
Probably some folks would shake their head and say, WTH, why not either check the forecast OR just leave it dripping. But data is my hobby, what can I say... if I have a chance to analyze a ton of data, plus learn a way to get my hands on tons of it (when I always have home insulation and degree-day concerns on my mind), plus finally make a nice simple rule of thumb for when I'm sleepily heading off to bed, well... I'm going to take it.
So it's not really home improvement, as much as home-life simplification. A very nerdy way to be lazy.
You asked.
