By Vince Condella Published Jan 15, 2003 at 5:04 AM

I'm not sure if this is going to make you feel warmer on a cold, blustery and bitterly cold winter day, but we are living under a new wind chill.

Actually this is the second winter of the new and improved wind chill factor. It gives us a more realistic indication of the cooling power of the wind and the cold. And that's all wind chill really is, simply an indication to us of the speed at which our bodies will chill down under various weather conditions. Strong winds and low temperatures are the main culprits in bringing our body temperature down from the normally cozy 98.6 degrees Fahrenheit.

The improvement in the new wind chill is based on a more realistic wind speed and a more realistic model of the human body. Wind speeds are typically recorded at National Weather Service observation sites by using an anemometer mounted on a pole about 30 feet in the air. Since none of us live at that height, measures were taken to estimate the wind speed at the 5-foot height. That speed is usually less than at the taller height.

The heat loss of the body is now more accurately calculated based on computer simulations and models of the human face. Overall the wind chill temperatures now are warmer than they were under the old system. A 30-mile per hour wind with a temperature of 5 degrees now yields a wind chill of -18 degrees compared to the old wind chill temperature of -41.

How can we use wind chill to our best advantage? Whenever the wind chill temperature drops below zero, a yellow caution flag should go up in your mind. Dress appropriately for the cold, especially if you are going to be out for more than five minutes. Remember to cover your head because we lose so much heat out of the top of our head. Adding a hat to our winter wardrobe helps trap more warmth inside our body.

A wind chill temperature below -20 should put up the red flag in our mind. Be very careful when venturing outside and be extra mindful of covering exposed skin. Our skin can freeze quickly if exposed to such cold wind chills.


Some people feel that this whole wind chill business is just something made up by the media to create more excitement in weather coverage. Wind chill has been around for decades, developed in 1939 by Paul A. Sipel, an Antarctic explorer and an expert on cold climate. He originally measured the time it took various containers of water to cool under various wind and temperature conditions, and then applied that data to develop an empirical formula.

Remember that wind chill only applies to living things, not inanimate objects. No matter how cold the wind chill, your car's radiator will only cool to the actual air temperature. If the radiator is protected down to -35 degrees, you'll be fine, even on those rare days when the wind chill reaches 50 degrees below zero. A strong, cold wind will cool the radiator quickly, but never lower than the air temperature.

Another term you may hear during the winter months is "heating degree days." This shows up on your energy bill each month and is a way for us to quantify the amount of energy we might use to heat our home.

A heating degree day is computed by subtracting the daily average temperature from the number 65. With a high of 28 and a low of 12, the average for the day is 20 degrees. That would yield 45 heating degree days. Add that up for the month and compare it to "normal" to see how your energy bill may be affected.

November of 2002 saw nearly normal temperatures and therefore nearly normal heating degree days. Last month was a little warmer than normal and the heating degree days numbered around 10% lower than normal. All things being equal, we would expect our December energy bill to be around 10% less than a normal December bill.

The "all things being equal" is the kicker here. Each of us heats our home differently. We set the thermostat differently; the energy efficiency of our homes is different, etc. So heating degree days is just a simple guideline, but one that is used frequently.

The calculations of wind chill and heating degree days are mathematically precise, but the concepts are subjective. Each of us perceives cold differently, and energy use is unique to each household. These parameters are just another way to measure changes in the atmosphere and how nature affects our lives and our pocketbooks.