Warmth is a stat that determines the player's ability to resist cold.
Unlike other stats, there is no method of viewing current warmth, other than adding the values on currently equipped armor (as of Beta v. Enraged Koala). The player's default warmth is 0, which can be increased through Armor.
With low warmth, the player's temperature meter will quickly begin to drop at night and in cold environments, forcing them to take refuge next to torches and campfires. Higher warmth will allow the player to face these environments without the need for additional heat sources. (Players cannot be negatively affected by high warmth, ie: "overheat.")
The Warmth Icon represents the value by which a specific piece of armor will increase the player's warmth, thereby increasing cold resistance.