Homeostasis! This is a pillar of human biology.

There are several systems working entirely independent from each other.

The system responsible for keeping you at normal temperatures will act independently. Weather you are sick, exercising, or spending the day at the beach— if you are hot, it wants to turn it down. It’s toolbox includes things like sweating or sending out chemicals. The hotter you get, the more this system will ramp up to turn it off.

The immune system will also act independently. Thankfully, the immune system is very smart and can learn when to use its tools, including inducing a fever. The tools of the immune system and how it’s used is an entire field of study.

Whether it’s the course of an illness or walking in and out of shade on a hot day, your body systems will compete with stronger and weaker signals depending on how important system feels it needs to use their toolbox.

Understanding how each system works and being able to identify when things go out of whack is pretty much the field of medicine.