How is wind chill calculated?

Heat stress is a commonly recognized problem. And while the struggle to protect workers from the heat continues, many employers have comprehensive heat protocols in place to reduce the risk of heat-related illness on their jobsites.

Cold stress doesn't get the same attention, however. Yet, cold stress can can result in a number of conditions have a devastating impact on the health and wellbeing of employees, including frostbite, trench foot, and hypothermia.

(Learn more about it in Cold Stress: Your Winter Safety Guide)

The first step to managing cold stress is to fully understand the hazard. Not only its effects, but also the factors that can increase the risks.

One of these is the wind chill.

What Is Wind Chill?

Wind chill refers to the effect of ambient air temperature combined with wind speed. The faster the wind and lower the temperature, the colder the air will feel against the skin.

Since there are only two factors involved, calculating wind chill is relatively straightforward. The easiest way is to simply refer to this comprehensive table created by the National Weather Service.

Below the chart, you'll notice the formula used to arrive at these calculation:

Wind chill (°F) = 35.74 + 0.6215T -35.75(V0.16) + 0.4275T(V0.16)

Advertisement

T = air temperature in degrees Fahrenheit (°F), and

V = wind speed in miles per hour (mph)

Anyone doing outdoor work or supervising outdoor workers in cold environment should pay attention to weather conditions and take additional precautions as it gets colder. Understanding how wind chill works will help ensure that the right measures are in place, since it provides a better approximation of the cold than temperature alone does.

Since wind chill is concerned with wind speeds, it isn't a relevant consideration for indoor work environments.

Steps to Prevent Cold Stress

OSHA recommends providing outdoor workers with more frequent breaks and opportunities to warm up as temperatures get lower and winds get stronger.

Moreover, when the windchill factor is severe enough, outdoor work should cease entirely (with the exception of emergency work. For instance, with no wind, temperatures of –45°F or lower are considered unsafe for all employees. Likewise, a temperature of –25°F with wind speeds above 20 miles per hour is simply too risky.

(Learn more in A Primer on Administrative Controls)

Precautions against cold stress range from providing high-quality protective weather gear to increasing the number of breaks per shift. Other important steps that employers can take include:

• Being aware of up-to-the-minute weather information
• Educating employees about the symptoms and warning signs of cold stress
• Training workers on first aid for cold stress
• Implementing engineering controls
• Provide workers with adequate personal protective equipment (PPE)

Workers who show signs of cold stress should be stabilized and then see a medical professional.