Wind Chill

Just as there are persistent hot places around the world, there are persistent cold places. The cold air alone can be deadly but when the air is moving if feels much colder. The wind chill is the effect of the wind on people and animals. The wind chill temperature is based on the rate of heat loss from exposed skin caused by wind and cold and is to give you an approximation of how cold the air feels on your body.

As the wind increases, it removes heat from the body, driving down skin temperature and eventually the internal body temperature. If the temperature is 0°F (-18°C) and the wind is blowing at 15 mph (13 kts / 24 kp/h), the wind chill temperature is -19°F (-28°C). At this level, exposed skin can freeze in just a few minutes.

The only effect wind chill has on inanimate objects, such as car radiators and water pipes, is to shorten the amount of time for the object to cool. The inanimate object will not cool below the actual air temperature. For example, if the temperature outside is -5°F (-21°C) and the wind chill temperature is -31°F (-35°C), then your car's radiator temperature will be no lower than the air temperature of -5°F (-21°C).

The Wind Chill Chart

To determine the wind chill temperature, find the value closest to your outside air temperature. Find the value that most closely represents your present wind speed. Your wind chill temperature is the value where lines drawn from the air temperature and wind cross.

Wind
(mph)
Temperature (°F)
40 35 30 25 20 15 10 5 0 -5 -10 -15 -20 -25 -30 -35 -40 -45
5 36 31 25 19 13 7 1 -5 -11 -16 -22 -28 -34 -40 -46 -52 -58 -63
10 34 27 21 15 11 3 -4 -10 -16 -22 -28 -35 -41 -47 -53 -59 -66 -72
15 32 25 19 13 6 0 -7 -13 -19 -26 -32 -39 -45 -51 -58 -64 -71 -77
20 30 24 17 11 4 -2 -9 -15 -22 -29 -35 -42 -48 -55 -61 -68 -74 -81
25 29 23 16 9 3 -4 -11 -17 -24 -31 -38 -44 -51 -58 -64 -71 -78 -84
30 28 22 15 8 1 -5 -12 -19 -26 -33 -39 -46 -53 -60 -67 -73 -80 -87
35 28 21 14 7 0 -7 -14 -21 -27 -34 -41 -48 -55 -62 -69 -76 -83 -89
40 27 20 13 6 -1 -8 -15 -22 -29 -36 -43 -50 -57 -64 -71 -78 -84 -91
45 26 19 12 5 -2 -9 -16 -23 -30 -37 -44 -51 -58 -65 -72 -79 -86 -93
50 26 19 12 4 -3 -10 -17 -24 -31 -38 -45 -52 -60 -67 -74 -81 -88 -95
55 25 18 11 4 -3 -11 -18 -25 -32 -39 -46 -52 -60 -67 -74 -81 -88 -95
60 25 17 10 3 -4 -11 -19 -26 -33 -40 -48 -55 -62 -69 -76 -84 -91 -98
Frostbite
times
None >2 hours ≤30
minutes
≤10
minutes
≤5
minutes

What is important about the wind chill besides feeling colder than the actual air temperature? The lower the wind chill temperature, the greater you are at risk for developing frost bite and/or hypothermia. Hypothermia occurs when body core temperature, normally around 98.6°F (37°C) falls below 95°F (35°C). Frostbite occurs when your body tissue freezes. The most susceptible parts of the body are fingers, toes, ear lobes, and the tip of the nose.

I addition to the wind chill the chart above shows the approximate times for the onset of frostbite. Note that while no frostbite can occur with air temperatures above freezing regardless of wind speed hypothermia is still a danger. You will also notice how the wind speed affects the onset of frostbite.

For example At -40°F and wind speed of just 5 mph, frostbite can occur in 10 minutes or less. Yet at a relatively higher temperature of -5°F frostbite is a threat still in 10 minutes or less with a 35 mph wind speed. This is because of the wind's ability to remove heat. Therefore, you cannot just rely on the wind chill value alone to determine your risk of frost bite.

Staying Warm

When your body temperature sinks below 96°F (36°C), you have hypothermia. prolonged exposure to temperatures as warm as 60°F (16°C), particularly in water, can trigger hypothermia if you are not properly dressed. Of the 28,000 people hypothermia kills yearly, most are seniors, according to the National Institute of Aging, but everyone needs to be careful.

Some medicines, problems with circulation, and certain illnesses may reduce your ability to resist hypothermia. As you age, your body becomes less efficient at letting you know when you are too cold. In addition, older people tend not to shiver effectively, one of the ways the body warms itself up.

Remember these tips to help prevent hypothermia:

  • Dress in layers
  • Wrap up well when going outside in the cold.
  • Avoid breezes and drafts indoors.
  • Eat nutritious food and wear warm clothes to ward off winter chill.
  • Wear a warm hat in the winter.
  • Eat hot foods and drink warm drinks several times during the day.
  • If you live alone, ask a family member or neighbor to check on daily.

If your temperature is 96°F (36°C) or less, you feel cold and sluggish, or are having trouble thinking clearly, see your doctor immediately or go to the nearest emergency room. It's better to be overly cautious than to die of a disorder that does not have to be deadly.

Degrees of Frostbite

Frostbite happens when the body's survival mechanisms kick in during extremely cold weather. To protect the vital inner organs, the body cuts circulation to your extremities: feet, hands, nose, etc., which eventually freeze.

  • First degree: Surface of skin is frozen, called frostnip.
  • Second degree: The skin may freeze and harden, blisters form in a day or two.
  • Third degree: Muscles, tendons nerves and blood vessels freeze.
  • Fourth degree: Pain lasts for more than a few hours and skin may develop dark blue or black. Gangrene is a real threat and will require amputation of extremities if occurs.

To avoid frostbite, stay inside during severe cold, especially when the wind chill is -50°F or below. If you must go out, try to cover every part of your body: ears, nose, toes and fingers, etc. Mittens are better than gloves. Keep your skin dry. Stay out of the wind when possible. Drink plenty of fluids since hydration increases the blood's volume, which helps prevent frostbite.

Avoid caffeine, alcohol and cigarette. Caffeine constricts blood vessels, preventing warming of your extremities. Alcohol reduces shivering, which helps keep you warm. Cigarettes shuts off the blood flow to your hands.

Fast Myths

Myth: You do not need sunscreen in winter.
Fact: We are actually closer to the sun in the Northern hemisphere winter so more radiation is reaching us from the sun. Also, snow cover reflects skin damaging radiation thereby magnifying the danger.

Myth: The body losses most of its heat through the head.
Fact: The body looses it heat generally in proportion of exposure. The surface area of the head counts for about 7% of the total body coverage and looses heat at about the same rate as any other 7% of the body that is exposed to the cold.

Myth: Cold air will give to a cold.
Fact: There may be other extenuating circumstances that can lead to a cold but just going outdoors without a coat does not directly increase your change of contracting a cold.