Hypothermia is one of the greatest threats to people participating in outdoor sports,
such as walking, mountaineering & sailing.
The particular risks include:

Cold and windy weather - windy conditions,
speed heat loss (wind chill).

Failing to wear suitable clothing and equipment.

Getting wet - water conducts heat away from the body
25 times faster than air.

Fatigue and exhaustion.

Dehydration - fluid levels, fluid loss and
heat loss are interconnected.