A Reader Asks: How do weather apps measure 'feels like' temperatures?
Winter weather can feel colder than it is. Also called wind chill, "feels like" temperatures factor in moisture, body heat loss and wind, an Estonian meteorologist explains.
Body heat isn't lost just because it's cold — wind accelerates heat loss, and the windier it is, the faster the body cools.
Taimi Paljak, lead meteorologist at the Environment Agency, explained that meteorologists calculate apparent or "feels like" temperatures using formulas that combine actual temperature and wind speed.
For decades, the standard was the 1939 "wind chill" index by Americans Paul Siple and Charles Passel, based on how quickly plastic bottles of water cooled in Antarctic conditions.
But people aren't water bottles. Factors like clothing, health and exposed skin affect how cold it actually feels. Rain or fog can also make it worse, since water conducts heat away from the body faster.
Canada introduced a more accurate formula in 2002, tested on real people and accounting more accurately for factors including body thermoregulation, skin properties and wind speed at a standard height.
The result is the modern wind chill temperature (WCT) index, which signals how quickly body heat is lost and helps prevent hypothermia.
This wind chill, or "feels like" temperature, is displayed in various weather apps and by the Estonian Weather Service (EWS). It can be used to determine how long it's really safe to stay outside with exposed skin under different conditions.
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Editor: Airika Harrik, Aili Vahtla
