Hypothermia:

Hypothermia could be a potentially dangerous drop in temperature, usually caused by prolonged exposure to cold temperatures. the chance of cold exposure increases because the winter months arrive. But if you're exposed to cold temperatures on a spring hike or capsized on a summer sail, you'll even be in danger of hypothermia.

Normal temperature averages 98.6 degrees. With hypothermia, core temperature drops below 95 degrees. In severe hypothermia, core temperature can drop to 82 degrees or lower.

Find out more here.

http://greatlakes.coastguard.dodlive.mil/2013/04/hypothermia-kills-these-tips-can-save-your-life/

https://www.betterhealth.vic.gov.au/health/healthyliving/hypothermia