The Wind Chill Factor
What It Really Means
There is a term often bandied about when the weather gets exceptionally cold, such as the single-digit temperatures we experienced in the final week of January. The Wind Chill Factor is a term that is frequently misunderstood and too often associated with sub-zero temperatures only. This Watoga Trail Report will start off with a short refresher course on the meaning of the Wind Chill factor.
Let’s start with an imaginary story that stars a couple of campers, Nancy and Dale. They decided that they liked camping so much in the summer months, they thought it might be fun to do a winter campout. They love camping and hiking at Watoga State Park but because the modern campgrounds are closed in the winter months, they opted for primitive camping over at the Laurel Run Campground.
Arriving in the late afternoon they immediately set about erecting their tent and getting organized. Nancy, being somewhat of a gadget gal, has brought an anemometer for measuring the wind speed and an outdoor thermometer for obtaining the ambient temperature, which is the current air temperature. She secured the anemometer on top of the campsite post making sure that nothing was blocking the wind.
She then hung the thermometer from a tree limb out of the sunlight which could heat the liquid in the thermometer affecting the displayed temperature. Then she pulled out the final piece of equipment from her pack, an electronic wind chill calculator.
After allowing time for the thermometer to obtain an accurate reading she wrote it down – the current ambient temperature at their campsite was 35 degrees Fahrenheit. She then took a reading on the anemometer; 15 miles per hour. According to the wind chill calculator the wind chill factor, or “effectual” temperature, was 25 degrees Fahrenheit. She entered this in her camping journal and she and Dale proceeded with making dinner and unrolling their sleeping bags in preparation for the long winter night ahead– who knows, they may be lucky enough to hear the melodic barks and yips of coyotes while snug in their tent.
Just before falling off to sleep Dale suddenly sits straight up and says that he had left their water bottles out on the picnic table, and if Nancy’s readings were accurate and the wind chill factor is indeed 25 degrees Fahrenheit, then the water would surely freeze. Nancy assured Dale that her readings were accurate but that unless the ambient temperature dropped, and the weather forecast did not call for this, their water would not freeze.
What Nancy knew was that the wind chill factor is based upon the heat loss experienced by living organisms by air movement, sometimes referred to as convective heat loss. The wind chill factor does not affect inanimate things in the same way; things such as water for example.
The ambient temperature, i.e. the thermometer reading, will not be affected by the wind, it will remain 35 degrees until such time as the ambient temperature drops or rises. So the wind chill factor will only affect their water in that it will bring the temperature of their water down to 35 degrees faster than if there was no wind at all, but it will NOT cause the water temperature to drop below 35 degrees.
On the following day, Dale and Nancy decide to hike the Ann Bailey Trail and they were expecting a wind velocity of 20 mph with an ambient temperature of 25 degrees. After checking the wind chill calculator Nancy tells Dale that they should dress as though the ambient temperature is 11 degrees rather than 25 degrees. So they will put on another layer of clothing including a windbreaker and wear their warmest mittens and head covering before venturing out on the Ann Bailey Trail for an enjoyable and safe winter hike.
The Wind Chill Factor is important because, in unusually low temperatures like we had last week, a person can experience frostbite on exposed skin within minutes if there is wind. Most outdoor enthusiasts know how to dress for these extremely low temperatures; it is in temperatures that are in the moderate range in which even experienced people can get into trouble.
Take for example the Great Greenbrier River Race of 2015 in which a number of race participants were treated for acute hypothermia on a day in late April. There are three legs to the race that includes running, paddling and cycling, all requiring a lot of exertion. At some point in the race, it started raining, adding to the moisture absorbed by the racer’s clothing from perspiration and paddle splash. Additionally, the cool air forced past the body while running, cycling and even paddling will carry away body heat, increasing the odds of becoming hypothermic.
The race is held each year on the last Saturday in April and in 2015 on that particular Saturday the ambient temperature was 41 degrees F. The racer’s clothing, already wet from perspiration while paddling, running and cycling, would be exacerbated by the rain and paddle-splash from the river. The wet clothing would increase heat loss by wicking away more body heat, something called conductive heat loss. Couple that with fatigue and you have the perfect recipe for acute hypothermia.
And indeed, approximately 30 people were treated for hypothermia during and after the race. The need for treatment was so great that additional ambulances were brought in to treat the race participants. Susan Chappell, a race participant, described her experience with hypothermia this way: “All of us were shivering uncontrollably when finished. It took me a full hour to stop shaking and my teeth from chattering, after having changed into dry clothes and huddled in the vehicle with the heat blasting.” And true to her spirit, she went on to say, “ Funny though, after all that, we were eager and excited to sign up for the next year’s race.”
In future Watoga Trail Reports, we will examine more closely the other cold-weather injury, frostbite. Frostbite causes tissue damage and eventually tissue loss, much like a burn. But frostbite is an effect of our body’s fascinating system to retain heat in the core of the body at the expense of other body parts such as the fingers, toes, and earlobes, thereby prolonging life.
Now to the trails and other activities at Watoga State Park:
After putting in a few hours of work on the Honeymoon and Pine Run Trails in preparation for the big Valentine Day Hike, I stopped by Watoga Lake to chat with the ice fishermen and fisherwomen. This turned out to be the highlight of my day as I walked from fishing site to site on a solid five inches of ice.
People of all ages were out on the ice jigging with PowerBait and catching trout. The rods used for ice-fishing are much shorter than standard fishing rods and the trick, as I found out, is to find the right depth and keep a close eye on your bobber, and it doesn’t hurt to jig the line from time to time to catch the eye of a passing trout.
Everybody out on the ice on Saturday morning was from the local area including one gentleman with a stringer of trout who calls nearby Seebert his home. Across the frozen surface of the lake were a dozen or so augured out holes as well as a couple of fabric ice-shanties. In addition to tending to their fishing holes, people were milling about engaging in conversations with friends and strangers alike.
If you picture ice-fishing as an exercise in being cold and miserable you might be surprised at the party-like atmosphere that develops on the frozen surface of Watoga Lake on a beautiful winter day.
Happy hiking and ice fishing, Ken Springer