system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Exercising warms your body and makes you feel hot. Fevers warm your body and make you feel cold. Why?

Does it have to do why core and exterior temperatures in the body, or what?
gpt
It is all about the temperature your body wants to be. When you are healthy, your body wants to be 37 degrees Celsius. If you work out, your temperature increases, while your body wants it to be colder, so you feel hot to signal you should cool down a bit.

When you are sick and have a fever your body wants to be way warmer than the regular 37 degrees to fight the infection. When your fever is rising, you will feel cold as your body wants you to be even hotter than you already were. You will notice that once you start getting better, you will feel hot; your body doesn't feel the need to be as hot any more so it signals you to cool down and you start feeling hot.