We were wearing identical clothing and I was jumping in water as well.
Actually, since I had this problem, I downloaded a couple mods and restarted the game a number of times. One time when I was outside, my temperature suddenly dropped to 30C, then slowly recovered. It seems to have been functioning normally since. It might have been related to admin rights or something! I was messing around with commands and may have accidentally done something. Seems to be working now though.
Thanks for the reply!