Running water at night when temperatures are below freezing

Question

I’ve been told to run the faucet furthest from the water meter at a slow trickle at night to prevent the pipes in our two story home from freezing (it’s about 5 degrees F where I am). Why do they recommend doing this at night only and not during the day—for example, when you’re away at work? If the temperature is below freezing both periods what is the difference? Wouldn’t you want to do this day and night?

In: Physics

Answer 1

Is this like an American thing? I live in a very cold winter climate (frequently – 40c) and have never heard of this before.

Answer 2

Worth noting that air temperatures are always measured in the shade. So while the thermometer might read the same at day and night, the ground temperature might vary more (because sunlight), and the pipes are in the ground.