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Boston Weather: 40.0°F | Fair


Wind Chilled Weekend

By Jonathan R. Moskaitis

The wind chill will play a prominent role in weather reports over the next five days, as New England becomes firmly lodged in a regime of cold, blustery conditions. Conceptually, wind chill quantifies the skin’s heat loss rate as a function of wind speed and air temperature, and thus is most naturally expressed in watts per square meter. However, in National Weather Service and media forecasts, it is typically expressed as a “wind chill equivalent temperature,” which is the still-air temperature at which the skin’s heat loss rate would be the same as it is for the ambient temperature and wind speed.

The history of wind chill calculations is a bit more interesting than one might expect. The original formulae were developed from data obtained during the U.S. Antarctic Expedition of 1939-41. Expedition members recorded the time it took for water in a small plastic bottle to freeze under different combinations of ambient air temperature and wind speed. From there, they calculated heat loss rates, assuming the rates were grossly similar to those of facial skin. This rather crude methodology was not updated until five years ago, when actual measurements of facial heat loss made on hardy Canadian volunteers supplanted the old plastic bottle values!

Extended Forecast

Today: Mostly sunny, windy. High: 36 F (2 C), Wind Chill: 23 F (-5 C)

Tonight: Clear and blustery. Low: 20 F (-7 C), Wind Chill: 6 F (-14 C)

Saturday: Light snow likely, especially in the afternoon. High: 31 F (-1 C), Wind Chill: 21 F (-6 C)

Saturday Night: Light snow likely early, then turning colder and windy. Low: 16 F (-9 C), Wind Chill: -3 F (-19 C)

Sunday: Cold and windy. High: 22 F (-6 C), Wind Chill: 5 F (-15 C)

Monday: Continuing cold and windy. High: 22 F (-6 C), Wind Chill: 4 F (-16 C)