Another thing that does seem to help is if you run into a pond or the ocean and get soaking status. I think it helps bring the temperature back down while still allowing you to wear the jacket or whatever.

As for realism, the military clothing actually should be a viable options for long distance running without overheating or freezing when not. That is how those clothes are designed to be while being blending you into the environment. I could also see Ghillie suites over heating you if you run in them, but they aren't in the game yet.

To be honest, when I had the message I was wearing a puffer jacket. However, the weather was the crazy DayZ rain system and it was raining a ton. My character even complained about it being "quite cold out there" while it was complaining about the over heating... So something is wrong. I never passed out, I stripped down ran into the rain and never dried myself off. The hyperthermia messages stopped at that time. I even abandoned the puffer and scrounged up another shirt somewhere else. I proceeded to run to another town and never saw another hyperthermia message. Maybe the issue is directly related to the puffer??

I can confirm this as well. I had messages about my character getting hyperthermia and it also said it was cold on the previous line. I will try to get a screenshot of this.

There is a suggested workaround of logging into a new server and then back to your original server at restart times. This could also be analogous to the timing of server restarts as suggested above. Waiting an additional 5 minutes from when you see the time of day increment could be required at least until this bug is fully resolved.

Added crash file upload.