Fever from exercising??

This happened last time I started working out too...
And no it's not just being hot from the actual exercise.
Both times this has happened, I exercised, then I felt really warm after. I thought it was just me getting hot from doing physical activity, but it didn't go away. I wet to sleep and woke up in the morning sweating. I took my temp and it's 100z

What casuses that?!?! And does that happen to anyone else?