How cold does it have to be to get frostbite?

Frostbite awareness: Stay safe in the cold

Wind and cold temperatures can cause frostbite in minutes, especially in areas like your fingers and toes. Here’s what to know.

As winter sets in, the combination of low temperatures and strong winds can pose serious risks to your health.

Frostbite can happen in minutes and can affect any exposed skin area, especially on your fingers, toes, nose and ears.

What is frostbite?

According to Mayo Clinic, frostbite is an injury caused by freezing of the skin and underlying tissues.

It occurs when the body's survival mechanisms kick in during frigid conditions. To protect vital organs, the body will cut blood circulation to extremities, which could eventually freeze.

The early stage of frostbite is called frostnip. It causes a cold feeling followed by numbness. As frostbite gets worse, the affected skin may change color and become hard or waxy-looking.

How cold does it need to be for frostbite?

Freezing temperatures cause frostbite. It needs to be colder than 32 F or 0 C for a person to get frostbite.

According to the National Weather Service, the lower the wind chill temperature, the greater you are at risk of developing frostbite. Wind speed can also affect the onset of frostbite.

A jogger runs to exercise in a frost-covered park on January 18, 2022. (Credit: TOLGA AKMEN/AFP via Getty Images)

This means the temperature may be significantly colder if there’s wind, which can increase your risk of getting frostbite.

The National Weather Service says that a wind chill index is a critical tool to help determine when conditions become dangerous, potentially leading to frostbite.

What is wind chill?

The wind chill is how cold the air feels on your skin when factoring in the wind for any temperature at or below 50 degrees with wind speeds above 3 mph.

A thin layer of warm air, produced by body heat, exists just above your skin. The wind strips this warmth away. As wind speeds increase, the amount of heat lost from your body also increases. Therefore, the stronger the winds, the colder the air will feel.

When winds are light – 3 mph or lower – the wind chill is not a factor because the thin layer of warm air stays close to your skin.

Wind chill index

This index accounts for the heat loss from the human body in cold, windy weather, using wind speed and temperature to assess the severity. For example, if the temperature is minus 5 degrees and the wind speed is 20 mph, the wind chill would be around minus 30 degrees. This means your body loses heat as if the temperature were actually minus 30 degrees, without wind.

Wind chills approaching minus 25 degrees or lower can lead to frostbite in as little as 15 minutes.

The National Weather Service developed the chart below to easily determine the wind chill.

Wind chill graph (Credit: National Weather Service)

Simply match the air temperature on the horizontal axis at the top with the wind speed on the vertical axis along the left-hand side, find where the two values intersect, and that number is your wind chill.

Signs of frostbite

Signs of frostbite can include the formation of ice crystals on your skin, as well as redness and/or pain in an area of exposed skin.

Numbness and skin that feels firm or waxy can also be a sign of frostbite.

Tips to survive cold weather

The National Weather Service says there are many ways to help protect yourself from the cold weather.

Stay dry: Wet clothing leads to rapid heat loss. Always wear waterproof, insulated boots.
Stay covered: Wear mittens or gloves, and cover your head. About half of body heat is lost if the head is exposed.
Dress in layers: Loose-fitting clothing traps air, providing insulation.
Stay informed: Keep a portable weather radio on hand to monitor conditions and warnings. Avoid unnecessary outdoor exposure on extremely cold days.