https://en.wikipedia.org/wiki/Wind_chill

Wind chill describes the difference between the measured air temperature and the perceived temperature as a function of wind speed.

Wind chill is defined for temperatures below 10 °C.

Purple fields have the potential to cause frostbite within 30 minutes or less. There is a risk of frostbite when the skin temperature reaches -4.8°C, below which frostbite occurs for about 5% of people.