Hypothermia

If you don't pack a hot water bottle.

Hypothermia is a cool mental disorder that is defined as body core temperature of humans being as lower than 35°C. The symptoms include shivering, mental confusion, hallucinations, getting naked and hiding inside or behind things.

Also, The Little Match Girl died this way.

Levels

Mild hypothermia

Mild hypothermia, or vanilla hypothermia, is when your body core temperature falls below 35°C but it's no lower than 32°C. The symptoms include shivering and mental confusion. It is not as bad as the ones mentioned below, hence it is vanilla. There is a high chance that most have experienced this but didn't even know since human body regulates temperature by itself.

Moderate hypothermia

Moderate hypothermia is when your body temperature is between 32° and 28°C. It is said that shivering stops when the body core temperature decreases but the confusion increases. Also hallucinations start. You imagine you're Leonardo DiCaprio in the film Titanic and are trying to share a raft with Kate Winslet.

Severe hypothermia

And the last one, Severe hypothermia is when you're very cool with a body core temperature of 20-28°C. Most people who have become as cool as this, start to get naked. It is thought that they feel hot. Severely hypothermic people love to play hide and seek with hallucinations while naked, they get tired and go to sleep.