Heat is a game mechanic that will help keep you alive. If you are in a Snow Biome, your heat will rapidly decrease. Your heat starts out at 100. If you do not keep your heat up, you will get the Cold debuff, which will reduce your speed by 5 every minute. You can keep your heat up using a Camp Fire. You do not want to be too hot or you wil get the Hot debuff, which will damage you by five every minute.