When the temperatures drop or the rain starts to fall, a good mountain bike jacket can keep you comfortable out on the trail.

Feels-like: wind chill When the air temperature itself is cold and the winds are moving at a higher speed, it can pull more heat away from the body and cause the water on our skin to evaporate faster.

The chart below from the National Weather Service shows how long frostbite takes for it to develop with varying wind speeds and temperatures.

The way meteorologists gauge the wind chill changed in 2001. First Alert Weather chief meteorologist Steve Beylon explains the wind chill chart in the video above.

The National Weather Service Wind Chill Chart uses a model dependent on heat loss from the adult human face during controlled experiments (children could not safely be used for such studies).

A wind-chill chart from the weather service shows that frostbite can occur within 30 minutes at a wind chill of 18 or 19 degrees below zero Fahrenheit.

Find the value closest to the temperature at the top of the chart and the wind speed to the left. Your wind chill temperature is the value where the imaginary lines drawn from the air temperature ...

This chart lets you estimate the wind chill without having to do the math yourself. Find the value closest to the temperature at the top of the chart and the wind speed to the left.

Wind chill chart shows when frostbite is a danger A chart from the Weather Service shows the relationship between temperature, wind and how long before frostbite occurs.

Wind chill chart shows when frostbite is a danger A chart from the Weather Service shows the relationship between temperature, wind and how long before frostbite occurs. The wind chill chart.