Not sure if everyone is on the same page regarding relative humidity. If you keep the amount of moisture (water) in a room constant and then heat the room, the relative humidity will drop due to the greater amount of water that warmer air can hold before condensing.
A mild example is take a 15 degree C (or 59 degree F) room at 40% relative humidity. Raise the temp in the room to 22 C (72 F) and the relative humidity will now measure about 26%, even though the same amount of water is still in the air.
This also means that cold air at 30% humidity is much drier than warm air at 30% humidity. Thus in colder weather, your skin can be much drier and prone to cracking.
A mild example is take a 15 degree C (or 59 degree F) room at 40% relative humidity. Raise the temp in the room to 22 C (72 F) and the relative humidity will now measure about 26%, even though the same amount of water is still in the air.
This also means that cold air at 30% humidity is much drier than warm air at 30% humidity. Thus in colder weather, your skin can be much drier and prone to cracking.