I’m not sure exactly what causes it, since there are several things going on in the scenario, but there’s a point where I feel extreme cold, which is great, but instead of just pain and penalties it causes actual physical damage to affected body parts, which doesn’t makes a lot of sense.
Yes extreme cold slows you dramitcally and causes damage. Running around naked in early spring is quite cold. Of course it’s intentional, it’s possible that you had a bad luck in regards to the weather and it was colder than normal as well.
I believe the OP is/was experiencing the fatigue issue, not general cold effects from lack of clothing or extreme temperatures.
Extreme fatigue has a secondary effect of causing cold regardless of clothing or local temperature and it can get bad enough to actually damage body parts and kill the player.
Recovering from infection for example is currently causing massive fatigue. I had the pleasure of recovering from infection recently and was rewarded with 6000 fatigue and -200 degree temperatures. For comparison 300 fatigue makes you ‘tired’. The weird temp effects causing damage is sporadic. In my case i only took occasional damage despite the indicator saying -200.