ELi5: Why does the weather feel much colder when the sun is out with a high UV index in the winter?
I think it’s also a psychological phenomenon. Your brain sees the sunlight and expect it to be warm but it’s still cold , this will make you feel colder than it really is.
Clouds hold in the UV light that passes through them, it kind of bounces around increasing the temperature. On a sunny day the UV just bounces off and goes straight back up.
Cloudless nights let heat escape into space, so the temperature plummets in the winter when it’s clear at night. Then it’ll be really cold the next day even though it’s sunny.
Then you get into a vicious cycle where cold temperatures suck out all the moisture and stop cloud formation, cooling you further.