What's up with wind chill?
Depending upon where you live, you might not pay much attention to the "wind chill factor". Folks in Florida tend to ignore it most of the year, but if you're in the Midwest or Northeast in January, then you'd better listen up!
The term "Wind Chill" means how cold it FEELS like regardless of what the temperature actually is.
When you use our wind chill calculator you'll enter the wind speed (V) in miles per hour and the air temperature (T) in either Farenheit or Celsius. Use the little drop-down list to make your choice. Then just click the "Find Wind Chill" button and your answer will magically appear. The calculator does all of the hard work, but let's take a closer look at those numbers that the calculator is crunching.
Speaking of calculators, you'll notice that we have two. One is labeled "New Wind Chill Calculator" and the other is labeled "Wind Chill". To understand why there are two, let's take a trip back to the 1940's where we find two guys named Siple and Passel poking around Antarctica looking for ways to figure out how cold it really is there. One of their experiments involved filling up a plastic jug and timing how long it took for the water to freeze under various wind and temperature conditions.
While they no doubt filled up several journals with their findings, I can cut it down to one sentence:
The lower the temperature and the harder the wind blew, the faster the water froze.
So I guess that you could say these two guys "discovered" wind chill. A lot of other people seem to agree and, in fact, the formula ended up being called the "Siple-Passel equation".
Their formula was a bit different than the one that we use today, and that's why we have the "old" and the "new" wind chill calculators.
The Siple-Passel equation said:
T(wc) = 0.0817(3.71V**0.5 + 5.81 -0.25V)(T - 91.4) + 91.4
The problem with the old method was that the calculations were based upon the wind speed as determined by an anemometer (device for measuring wind speed) which is usually atop a 10 meter pole. While crows and low-flying planes might care about the temperature and wind chill at that height, the average human stands much shorter and experiences different wind and temperature conditions at that reduced height.
So, some time around October of 2001 the U.S. and Canadian weather geeks got together and developed the "new" formula. This formula is based around, believe it or not, the human face which most everyone agrees catches the bulk of the wind when it blows your way.
The new formula to calculate wind chill is a bit intimidating and it looks like this:
WC=35.74+0.6215T-35.75(V**0.16)+0.4275T(V**0.16)
Where V=wind speed in MPH and T=temperature F.
The '**' represents an exponent or 'to the power of'.
The formula takes into consideration how much heat the skin of the face loses and other factors. For some insight into those "other factors" I turned to Denis Phillips, Chief Meteorologist at ABC Action News, who tells us:
"The new Wind Chill equation calculates wind speed at an average height of five feet which is assumed to be the typical height of an adult human face. It is based upon determining how much heat the human face loses when exposed to low temperatures with a wind speed greater than 3 MPH. There is no wind chill factor if the wind falls below 3 mph or when the temperature rises above 50F. Also, the Wind Chill assumes no impact from the sun."Thanks Dennis, now could you tell us why we care about the wind chill factor? Is there any real danger to the human body due to what the temperature "feels" like versus what it actually is?
"Well Blaine, the wind chill definitely does present a danger to us when we are outdoors. That's because the skin responds to the wind chill temperature just as if it were the real temperature. As a result, there is a risk of frost bite with a 30 minute exposure at -10F and below. That risk increases with just 5 minutes of exposure with a wind chill of -50 or lower."So there you have it. If it wasn't for those guys Siple and Passel, we'd probably still be walking around saying "Brrr, it certainly FEELS colder than the thermometer says." And we'd never know that we were right!
Note: Remember though that the highest temperature that can be entered is either 40 F or 6 C.