system
Given the following post, respond as if you're commenting on Reddit:
human
Why do I sleep so much better when it's cold, yet feel very tired when its hot?

And when it's very hot, I can't fall asleep at all.
gpt
Here's some educated speculation:
So, when you sleep, your body drops in core temperature. This is part of your circadian rhythm, and is triggered by a release of melatonin. This is to conserve energy during sleep. In a chilly environment, it is quite easy to drop your body temperature, and therefor easy to fall asleep.
In a hot environment, your body temperature might drop in order to maintain a healthy temperature. Since this effort by your body to drop your temperature is usually accompanied by sleeping, it might make you feel sleepy.
There might be some psychological things working in the background too, such as outside temperature being a cue as to when to sleep.