Wind chill warning

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A wind chill warning was a hazardous weather statement previously issued by both local forecast offices of the National Weather Service (NWS) in the United States and by the Meteorological Service of Environment and Climate Change Canada (ECCC) when wind chills were forecast to reach values low enough for residents and travelers to be susceptible to life-threatening medical conditions (such as severe frostbite and hypothermia) or death associated with accelerated body heat loss. In both Canada and the United States the "wind chill warning" has been replaced with the "extreme cold warning."

Extreme wind chills meeting wind chill warning criteria can generate a significant decrease in body temperature, and induce frostbite damage to exposed skin and other tissue over an accelerated period of time (onsetting within as little as 10 to 15 minutes in severe cases). People within the warned area are advised to avoid venturing outdoors unless conducting necessary travel; if going outside, extra precaution should be taken against the likelihood of developing hypothermia and frostbite by wearing multiple layers of clothing (such as a thick winter coat, a scarf and long underwear, in addition to layers of outerwear) as well as a hat (e.g., a knit cap that can be used to cover the ears) and gloves.^[1]

In the United States, the exact definition varies from state to state or between National Weather Service county warning areas (with the highest criteria in the Upper Midwest and Alaska, and the lowest criteria in the Florida Peninsula), and a warning is used to express more severe conditions than a wind chill advisory.^[1] If extreme wind chills are expected to quickly lead to frostbite or death, then enhanced wording with the words particularly dangerous situation may be added to the text; this is rarely issued. The National Weather Service in Twin Cities/Chanhassen was the first office to do this on Sunday, January 5, 2014.^[2]

As of April 8 2014, Environment Canada replaced the Wind Chill Warning with an Extreme Cold Warning. The warning is still issued based on a region's normal climate. In the older system a wind chill warning for Southern Ontario and Atlantic Canada was issued when the wind chill dropped to -35. This meant that if the temperature was −37 °C (−35 °F) with no wind a warning was not issued. Under the new system the extreme cold warning is issued based on either the temperature or the wind chill being a certain value for at least two hours. The values range from −30 °C (−22 °F) in the south to −55 °C (−67 °F) in parts of the Arctic.^[3][4]

In the United States, as of October 2024, the "wind chill watch" and "wind chill warning" were, among other changes, eliminated in-favor of a "simplified" naming scheme, with "wind chill warning" becoming "extreme cold warning."