Players get overheated regardless weather, time of day, dressed or naked, dry or wet or submerged into water, outdoors or indoors and cooling down process is completely off too. I get overheated constantly (even early in the morning, wearing t-shirt, hunting camo trousers, military boots, cowboy hat... moving slowly outdoors) Last time I found myself nice remote lake, undressed, hopped into water, submerged and guess what - still rapidly overheating. 10 minutes like that and then I got message I am cooling off, but my stats still reads "Overheated". Put my clothes on, let them soak too, sit, then swim again, undress and swim again, no change - still "Overheated".
Guys, IRL if you walk outdoors in summer wearing similar gear like in the game, sure you get sweaty, but don't tell me that if you then stop to undress your shirt and drink water you don't cool down within a minute or two. And immediately when jumping into water, or walking "drenched" on fresh air. Really.