It's about to get downright frigid in North Texas.
A cold front will move through Dallas-Fort Worth Saturday. The weather service issued a cold weather advisory for Collin, Dallas, Denton, Ellis, Kaufman and Tarrant counties that will last from midnight Saturday night to Sunday at 9 a.m.
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ERCOT issued a weather watch for Monday through Thursday, "due to extreme cold weather across the ERCOT region, higher electrical demand, and the potential for lower reserves."
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Sunday, Monday and Tuesday's morning wind chills will be in the single digits and teens, according to the weather service.
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Here's what you need to know about wind chills:
What is a wind chill?
Wind chill is the "the temperature it 'feels like' outside and is based on the rate of heat loss from exposed skin caused by the effects of wind and cold," as defined by the National Weather Service.
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As wind speeds increase, the body cools faster and skin temperature drops, according to the weather service. Wind chill affects only living things because inanimate objects cannot get colder than the temperature outside.
How are wind chills determined?
To calculate wind chills, meteorologists use a formula that factors air temperature and wind speed. The formula can get complicated, but this chart shows the drastic effects wind can have on how cold it feels.
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It doesn't take strong wind to make it feel much colder than a thermometer shows. For example, 35 degrees with 15-mph wind can feel 10 degrees colder.
AdvertisementWhy do we calculate wind chills?
Other than as a point of reference to give people an idea how cold it feels outside, the National Weather Service uses wind-chill value to know when to issue warnings about conditions that are potentially hazardous or life-threatening.
For example, the wind-chill chart shows how long a person can be exposed to cold, windy conditions before frostbite develops. On a day when it's 0 degrees with 15-mph wind, the wind chill is -19 degrees. Someone outside would have 30 minutes before frostbite could start to develop.
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In Dallas-Fort Worth, where the average winter lows range in the mid- to upper 30s, frostbite conditions are rare.
Who came up with wind chills?
The United States and Canada previously used a wind-chill index based on the 1945 research of Antarctic explorers Paul Siple and Charles Passel. Siple and Passel hung a container of water from a pole and measured the cooling rate of water. But water freezes faster than flesh, which is why the National Weather Service came up with a new index based on heat loss when skin is exposed to cold air.
In 2001, a group of U.S. and Canadian researchers conducted trials on 12 volunteers inside a chilled wind tunnel, according to the weather service. In the trials, heat flow was measured from the volunteers' cheeks, foreheads, noses and chins, as they walked at 3 mph on a treadmill for four 90-minute periods while they were exposed to different wind speeds and temperatures.
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The experiments allowed researchers to develop a wind-chill index with more accurate measures of what blustery winds will feel like to a human.
The National Weather Service offers the following tips to stay warm in cold weather:
Wear layers of loose-fitting, lightweight, warm clothing. Trapped air between the layers will insulate you. Outer garments should be tightly woven, water repellent and hooded. Wear a hat, because much of your body heat can be lost from your head. Cover your mouth to protect your lungs from extreme cold. Mittens, snug at the wrist, are better than gloves. Try to stay dry and out of the wind.Advertisement
Staff writer Lana Ferguson contributed to this report.
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