The thermometer outside our kitchen window said 18 degrees when the kids left for school this morning. The wind has picked up since then. Our local weatherman told us to expect winds between 20 and 30 miles an hour this afternoon at 2,000 feet. (We’re at 1,500 feet.) According to the Wind Chill Index on the National Weather Service website, that means that when Ursula and Virgil come home this afternoon, the wind chill temperature — the way it feels — will be somewhere between 1 and 4 degrees.
Ursula looked up the Wind Chill Index earlier this month as part of a report on cold-weather safety for her health class. She learned that the first wind chill chart was created by scientists in Antarctica who tracked air temperature, wind speed, and the effect of both on water in a plastic bottle. Scientists now track the effects of wind and cold on human subjects, but the basic notion of wind chill has stayed the same: Wind makes the cold feel colder, makes water freeze faster, and makes us freeze faster, too.
Ursula learned that our bodies have a couple of built-in defenses when we become cold. When the body first encounters cold temperatures, it shuts down (constricts) some of the blood supply to the body’s surface, which allows it to concentrate on warming the inner core, where the heart and other vital organs are located. That, along with their distance from that vital core, is why our hands and feet often give us our first signs that we’re cold.
The body’s second defense, up to a certain point (or I should say, down to a certain internal temperature) is to make us shiver. This involuntary muscular activity creates as much body heat as a slow jog or the caloric heat that comes from eating two chocolate bars.
If we don’t listen to the body’s warning signs, or if we’re unable to respond to them, we can get frostnip (superficial frostbite, usually to toes, fingers, or face), frostbite (deeper freezing of tissues), or hypothermia (our internal body temperature falls). If our core body temperature falls below 95 degrees, we stop being able to produce enough heat on our own and need other help — other people’s warmth, warm food and drink — to survive.
But there are lots of things we can do to stay safely warm in cold weather, like the tips that Ursula collected for her report:
• “If your feet are cold, put on a hat.” That old saying is true. We can lose 40% of our body heat from an uncovered head.
• Wear layers. Layers of clothing trap the warm air created by our bodies. Another old and true saying: “Wear two pants, not thicker pants.”
• Wear wind protection. Wind sweeps away that nice warm layer.
• Wear wool or polypro instead of cotton, mittens instead of gloves. Keep your boots dry and at room temperature, not the temperature outside. You can lose several degrees of body temperature just by putting on ice-cold boots.
• Eat, drink, and don’t get exhausted.
• Listen to what your body is telling you. Go inside to warm up!
Thursday and Friday it’s supposed to be even colder here, down around zero degrees, and also windy. If the breeze is even 15 miles an hour, the wind chill will be –19. That's 19 degrees below zero. The wind chill chart identifies a risk of frostbite after 30 minutes of exposure in such conditions. Ursula’s school keeps students indoors when either the air temperature or the wind chill drops below 10 degrees, so I think we’re looking at indoors play the rest of the week...
The National Weather Service has an updated wind chill index and lets you enter temperature and wind speed to determine a specific wind chill.
“Great Kids, Great Outdoors” is an AMC Outdoors blog, written by Kristen Laine.
Labels: cold, frostbite, hypothermia, Kristen Laine, safety, wind, wind chill