This does not happend every day of temperate season. For example, it is day 268 in hamlet in my world, almost beginning of the day (2 segments of day), i hold thermal stone and i overheat. I do not stay near campfire or anything, also thermal stone colour is grey (middle temperature, neither cold nor warm), which is very odd. This overheat can last very long, but after i drop thermal stone on ground, it quickly goes away. I never overheat in hamlet if i do not hold thermal stone. Also, the same bug exists in shipwrecked.