Some people talk about the weather when they have nothing else to talk about, whereas climbers and cyclists and runners and skiers, etc. talk about it all the time – as it plays a crucial role in their adventures. Weather patterns affect everything from the clothes they wear, the gear they bring, and when they head out. Recently, SLATE.COM posted an article about the Wind Chill Factor being somewhat deceptive and outdated. Apparently, for the past 60 years, the windchill factor has been grossly exaggerated, and a new “toned down” system has been created that is more accurately calibrated with the effects of the wind.

In it´s simplest form, the Wind Chill Factor means that whatever the temperature is outside, it is going to feel colder in windy conditions. To this day there are no instruments that measure the wind chill factor as it is merely a sensation felt by human skin, and since 1945 we have been using a formula derived by two Polar Explorers: Paul Siple and Charles Passel. According to SLATE, “the two men left plastic bottles of water outside in the wind and observed the rate at which they froze. The equation they worked out used the wind speed and air temperature to describe the rate at which the bottles gave off heat, expressed in watts per square meter.”

In other words, it is a way to determine the rate of heat loss in watts per square meter and correlate it to a rate produced without influence of the wind – AND SO – in 30mph winds, 5 degree weather could match the rate of heat loss in -19 degree weather with little wind. Below certain temperatures we lose heat from our skin faster than our body can warm it. At around -13 deg. Farehnheit your skin will begin to freeze, and at -35 degF your skin will freeze in minutes.

The Old Wind Chill Chart

In 2001, scientists had come up with a more accurate system to account for the wind chill factor, largely because it took into account the human body, since they can play a huge role in how we are able to cope with the cold – i.e. a tall slim build will suffer more from the cold than a short round figure. Two scientists, Osczevski and Bluestein, modeled heat loss using the approximate size and shape of the human face considering that the face would be the most exposed part of the body, and would reflect heat losses more accurately than would the shape of a bottle (and the face would be most exposed while bundled up and the source of most heat loss). They also assumed a baseline wind speed of 3mph to reflect the average walking speed (the old equation used 4 mph). Lastly, since different skin types respond differently to the cold, they factored the equation to address the skinny body types that would be most affected by the cold.

New Wind Chill Chart

Daniel Engber, the author of the article proposes that we eliminate altogether the wind chill factor, claims that after three decades of practice we have already gotten used to translating the outrageous numbers associated with WCF, and instead of switching to the new system, he suggests we just drop the WCF altogether.

Daniel writes, “The best algorithm we’ll ever have for determining how cold it feels comes from our own experience. A look out the window gives us most of the variables we need to compute our own, personal weather index. The sight of a few leafy trees will tell us how windy it is on our corner and whether the breeze is swirling or gusting. We’ll see if the sun is shining or if the sky is overcast. We’ll also know how we’re dressed, how tall we are, how much we weigh, and how quickly we walk down the street. We can even stick our hand outside for a moment, to get a sample of the ambient air temperature.
That’s more than enough data to know how it might feel to step outside our front door.”

Yet, I can´t help but think, “Well, that might be alright if you are stepping out the door and into your dual climate controlled SUV, but what about somebody about to make a push for a summit, or who is packing gear for a 7 day trek or in regions with extreme weather changes. This info is crucial.”

It is great that a refined version of the wind chill factor has come about and it would be nice to see more weather channels converting to the new index. And sure, for the majority of people, like Daniel Engber, who love to talk about the weather, the wind chill factor isn´t very important – but for athletes and adventurers, advancements in weather forecasting and communication are always good news.

Related posts:

1. Facing the Wind