Wind chill is measured by the evaporation of perspiration. The stronger the wind, the more quickly your sweat evaporates, making you feel cold faster.
Until 2001, the wind chill factor was based on the work of Paul Siple and Charles Passel, two Antarctic explorers in the 1940s. Experimenting with water in plastic cylinders, they noted how long it took water to freeze under various temperatures and wind speeds.
But their system had some flaws. For one thing, the experiments were measured on winds 33 feet above ground. For another, human flesh is not plastic.
So, many years later, volunteers were recruited to wear temperature sensors on their faces, and tests were conducted at different wind/temperature combinations in a wind tunnel. This new wind chill factor, designed by the National Weather Service and the Meteorological Service of Canada in 2001, measures temperature, wind speed, and lack of sunlight to give a more accurate reading.
The new formula is actually warmer than the old one. Pre-2001, a wind speed of 55 miles per hour at five degrees above zero would result in a wind chill of nearly 50 below zero. Today, the same conditions result in a wind chill reading of closer to 30 below.
Wind chill affects how cold it feels outside, compared to how cold it actually is, because wind chill increases the rate of heat loss. As we get cold, our bodies conserve heat around our vital organs, which means pulling heat away from the extremities. This is why good mittens, boots, and a hat and scarf are so important.
However, it is possible to overdress for winter. Heavy clothing increases perspiration, which causes a cooling effect. By dressing in layers, you can shed them as you warm up. Avoid cotton hats and scarves, because cotton absorbs sweat, and take off wet clothing as soon as possible, because it greatly accelerates cooling.
Hypothermia sets in when your body temperature drops below 95 degrees. Symptoms include uncontrollable shivering, disorientation, sleepiness, and slurred speech. Wrap the person in a dry blanket and get them out of the cold, but avoid rapidly increasing their body temperature (e.g., no hot baths or showers), because it could induce shock. Seek emergency medical care.
Frostbite is, literally, frozen body tissue. Symptoms include numbness, tingling, pain, and changes in skin color due to restricted blood flow. Get to a warm place as soon as possible and avoid walking on frostbitten toes. Warm the affected area with lukewarm water or body heat, but do not rub or massage and don’t use heating pads, heat lamps, or open flame because frostbitten tissue is more vulnerable to burns. If warming the affected area doesn’t restore circulation, seek emergency medical care.
Wind chill is an even bigger headache if, like me, you suffer from Raynaud’s Syndrome, which is a circulatory disorder in the extremities that causes the small blood vessels in the fingers and sometimes toes to spasm when they lose heat. The result is a numb, tingling sensation with extremities turning white, then blue, then as heat returns, red, often followed by uncomfortable throbbing.
El Niño is upon us this year and, so far, the weather has been mild, but as we learned two years ago, Old Man Winter often has other plans. We might see snow and ice in the days leading up to the Winter Solstice, with a cloudy, cold Christmas and a cold start to 2016.