There is a phenomena I occasionally see on various sites that offer daily and hourly forecasts. In this case, I am using the weather underground (I hate their new format, btw.).
Anyway, to illustrate the problem, that the daily low according to the daily forecast for Wednesday the 17th, is 31F.
If you look at the hourly lows, the lowest temperature is 42F. That is a big difference. Can anyone explain to me why this happens and which is more trustworthy?
10 day forecast:
Hourly:
Probably it was overnight the night before? Usually the daily highs and lows are calculated from sunrise one day until sunrise the next. To basically fully encompass one day/ night cycle into a single days records. Looking at the graph it seems exactly what is going on.
Otherwise one really cold night would show up as the low for two consecutive days, and not really tell you what the nighttime is like.
That could explain it. Thursday morning is supposed to be super cold, so you are saying Wednesday’s low will be coming from Thursday morning?
I figured it was midnight to midnight.
Nope, more like 6am to 6 am.
Thanks. That is good to know.
In a slightly related question, how long does it take for water to freeze in a pipe? My house does have some water pipes exposed on the outside. Being in Florida, I am not sure what to worry about. It will be at freezing or a tad below for about 3 hours.
How exposed? Being in the tundra, I have had frozen pipes. But ours are built with understanding of cold weather, so it takes a week of temps at or near zero to even be a threat most of the time. So when you say exposed…
The reality is it is probably fine. But, to feel safe, perhaps turn the faucet on at a drip pace to keep water moving. 3 hours isn’t going to be enough if they have any insulation at all, but if it is literally metal pipe exposed to elements then a slow trickle would keep it from freezing over those short spans.
There isn’t any insulation at all. They are PVC pipes. They come out of the ground, and up the side of my house, and then go inside maybe 1 foot above the ground.
Huh, I didn’t know that was a thing before
Just to be safe open that faucet a bit. I doubt that’ll be cold enough or long enough to freeze, but this will make sure to prevent any real chance of trouble. If you’re feeling really worried you can take a few old towels or blankets and wrap it around the exposed pipe. But don’t sweat it. With the tap open, even if it starts to freeze, it shouldn’t burst.
Overnight low for a listed day is usually found just before sunrise on the following day. You can see it in your link on Thursday morning.