system
Given the following post, respond as if you're commenting on Reddit:
human
Why can I listen to a certain radio station only when outside temperature is really low (-20 C/ -4 F)?

It's the heart of winter here in Finland, temperatures around -20 C and stuff. I noticed that a certain radio station, which can not usually be heard where I live, has suddenly become available. 

So my question is: Do radio waves 'go further' in subzero temperatures and why does this happen? My friends speculated that the phenomenon has something to do with air humidity ('dry air') and thus electrical conductivity of air.
gpt
The ionosphere has a different composition at night then during the day due to the sun's rays not hitting it at night. Finland is very far North, and being the winter time the ionosphere is hit by very limited sun rays. The Ionosphere reflects certain radio waves, thus allowing you to hear stations from much farther away in the night time; which happens to be pretty much all the time if you live in Finland in the winter.