The parts directly related to what doctors worry about is here:
Once your core gets above about 104 degrees, you’re in serious danger. High internal temperatures lead to increased pressure in your skull and decreased blood flow to your brain. (Doctors diagnose “heatstroke” when the heat starts to affect your central nervous system.) Damaged tissue may also enter your bloodstream and lead to kidney failure. Very high internal temperatures—like 120 degrees—can destroy the cells in your body through direct heat damage.
The other parts are good too. Listen or Read!