Wind Chill

Wind chill is the perceived temperature your body feels when air temperature and wind speed are combined. The wind chill effect increases the rate of heat loss from exposed skin. Wind chill calculations show that the stronger the wind speed at a given temperature, the cooler the wind chill will be. For example, when the air temperature is 20°F and the wind speed is 15 mph, the wind chill is 6°F. If the wind speed doubles, the wind chill drops to 1°F.

Remember that cold stress does not only occur in below freezing temperatures. It can be brought on by more moderate temperatures in combination with high wind speeds and moisture. For example, if the air temperature is 40°F and the wind speed is 35 mph, your exposed skin receives conditions equivalent to the air temperature being 11°F. While it may be obvious that cold stress is a hazard in below freezing conditions, it is important to understand that it may be a hazard in warmer air temperatures as well.

Most workplaces are not equipped to accurately measure wind speed and air temperature, so employers should refer to local weather reports to monitor the wind chill. The following signs can be used to estimate wind speeds in the field:

• At 5 mph, a light flag will move slightly.
• At 10 mph, a light flag is fully extended by the wind.
• At 15 mph, the wind will raise a sheet of paper off the ground.
• At 20 mph, the wind is capable of blowing snow.

To learn more about Cold Stress Safety visit our Cold Stress, Illness & Injury Safety Online Training web page.