A refreshing breeze to deadly exposure, why do you “feel” the outside temperature? (Wind Chill)

Discussions on climate may be centered on the global atmospheric scale all the way down to the interesting microclimates linked with the urban heat island effect. We can go even one step further! How about where the weather and your body intersect? Our bodies have the hallmarks of a combustion engine since consuming calories (fuel) gets converted to useful energy (movement). Vitally, our biological energy conversion processes generate a stable life sustaining body temperature averaging near 98.6°F (37°C). This means your mere presence out in the world actually modifies the weather through both heat and moisture exchange with the environment. In reality the atmosphere exerts a much greater influence on you than the other way around! In the process the environment wants to reach temperature and moisture equilibrium with anything it touches, which can have dire consequences for us. In nature, energy and moisture will continue to transfer between any two “sources” until the imbalance is eliminated (just like how the outside air and a lake’s surface constantly interact or a cloud tries to survive in the sky).

So, let’s take a look at the meteorological term “wind chill” often mentioned in winter weather forecasts that relate to how you “feel” when walking outside. Wind chill, as the name implies, deals with feeling colder than what the thermometer says. What’s happening here is that as wind blows over your skin the colder air making contact saps and carries away your heat generation. The attempt for the body to modify the outside temperature for survival benefit is bested by wind continuously replacing the air in contact with your skin. Unless sufficiently insulated (clothes and shelter), it becomes a losing battle where your body can no longer maintain 98.6°F, which can lead to life threatening hypothermia and frostbite. The wind chill effect is amplified by evaporative cooling should you get wet and the air mass around you is particularly windy and dry. Keep in mind, temperatures above freezing but combined with stronger winds can still result in dangerous wind chills!

Refer to the NOAA National Weather Service Wind Chill Chart to see what your body "feels" under a range of air temperatures and wind speed thresholds. You might be surprised at how dangerous wind chill can be!

Photo Credit: Jonny William Malloy