From the DayZ Wiki:
Your body temperature will decrease when:
Remove clothing items.
Expose yourself to rain.
Take a dip in the sea, a lake or a pond - this makes your clothing items 'wet' or 'soaked' (fast)
You are outdoors at night (slow)
You are outdoors in a windy environment (slow)
The "fast" and "slow" indications refer to at what rate your status changes.
The wiki page also has useful information about getting warm:
You increase your body temperature by:
Sit beside a Fireplace (very fast)
Wear extra clothing items and or Make sure your clothing items are dry.
Expose yourself to sunshine or Remaining inside buildings. (slow - moderate based on time of day\night)
Descend to lower altitudes
Moving (very slow, faster movement speed will neutralize loss)
Regarding the issue with clothes not drying from sitting beside a fireplace; I actually experienced this recently and may have a solution. Most of my clothes were dry, but my shoes and face mask stayed Damp no matter how long I sat by the fireplace. So I took them off and placed them on the ground next to the fireplace, and voila! They became dry straight away.
I don't know if it's a bug (since the Damp status disappeared pretty much instantly) but it kind of makes sense that the clothing dries faster while drying "on it's own." Might also be that the status just has become "stuck" on the item and you need to drop and re-equip the item for the correct status to show.
The easiest solution to getting rid of Hot status I can think of would be: go for a swim or walk around in the rain for a while to get wet and Hot status will eventually disappear. Afterwards, remember to wring out your Wet clothes to make them "just" Damp. Then use a fireplace to dry up. Optionally take off clothes and put them on the ground by the fireplace to (maybe) have them dry up faster.