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An extreme cold warning is a weather warning issued by Environment and Climate Change Canada (ECCC) and by the United States' National Weather Service (NWS) to inform the public about active or imminent severe cold temperatures in their local region.
As of April 8, 2014, ECCC replaced the "wind chill warning" with an "extreme cold warning." In the older system a wind chill warning for Southern Ontario and Atlantic Canada was issued when the wind chill dropped to -35. Thus a temperature of −37 °C (−35 °F) with no winds would not require a warning be 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 warm temperates to −55 °C (−67 °F) in parts of the Arctic.[1][2]
As of 1 October, 2024, the NWS replaced the "wind chill warning" with the "extreme cold warning." The standards governing issuance are set by local NWS offices. The 'step' below an extreme cold warning is an "extreme cold watch," which itself replaced the "wind chill watch" in October 2024. [3][4]
An extreme cold warning is issued when the following temperatures are expected to last for at least two hours, which different regions have different criteria for:[2]
- South-Central Ontario and Southwestern Ontario issued at −30 °C (−22 °F)
- Southeastern Ontario, the Southern Interior of British Columbia, the British Columbia Coast and Atlantic Canada (excluding Labrador) issued at −35 °C (−31 °F)
- Quebec (excluding northern Quebec) issued at −38 °C (−36 °F)
- Northern Ontario (excluding the far north), Central Interior of British Columbia and the Prairies (Alberta, southern Manitoba, southern Saskatchewan) issued at −40 °C (−40 °F)
- Far northern Ontario, northern Manitoba (excluding northeastern Manitoba), northern Saskatchewan, Northern Interior of British Columbia and Labrador issued at −45 °C (−49 °F)
- Northern Quebec (excluding Nunavik) issued at −48 °C (−54 °F)
- Yukon, Northwest Territories (excluding Paulatuk, Sachs Harbour, Ulukhaktok), Baffin Island, and northeastern Manitoba issued at −50 °C (−58 °F)
- Nunavik issued at −52 °C (−62 °F)
- Northwest Territories (Paulatuk, Sachs Harbour, Ulukhaktok only) and Nunavut (excluding Baffin Island) issued at −55 °C (−67 °F)
In the United States an extreme cold warning was an experimental weather warning issued by the National Weather Service in North Dakota, South Dakota, and Minnesota.[5] The warning was issued if the temperature fell to −35 °F (−37 °C) or colder with a wind of less than 5 mph (8 km/h; 2 m/s).[6] It was an experimental advisory for when the air temperature was dangerously cold, but the wind was too little to warrant a Wind Chill Watch or Warning.[7]
The Extreme Cold Warning was used from January 10, 2011 to April 15, 2011.[8] It was discontinued beginning with the 2011-12 winter storm season. Only five Extreme Cold Warnings were issued in that period: one for Burleigh County, three for areas outside of the Bismarck–Mandan metropolitan area, and one for West Glacier, Montana[9]
In a partner webinar on October 30, 2018, the National Weather Service announced that based on survey feedback, the Extreme Cold Warning and the Wind Chill Warning will be consolidated into the Extreme Cold Warning, meaning that this product would once again be issued on a regular basis. This change was hinted to take effect sometime in 2021, accounting for NWS software upgrades.[10][11] This was confirmed at the AMS 2024 meeting in January 2024.
In October 2024, the NWS officially implemented these changes to its wind chill and hard freeze warnings, watches, and advisories (WWAs) as part of its "Hazard Simplification initiative." The goal of these WWA name changes, per the NWS, is "simplifying a suite of cold weather forecast products to improve messaging of winter hazards and provide better decision support." The changes include:[12][13]
Extreme Cold Consolidation and Renaming
- Wind Chill Watch was renamed to Extreme Cold Watch
- Wind Chill Warning was renamed to Extreme Cold Warning
- Wind Chill Advisory was renamed to Cold Weather Advisory
Freeze Consolidation
- Hard Freeze Watch was renamed to Freeze Watch
- Hard Freeze Warning was consolidated to Freeze Warning
Local NWS offices will still determine the standards governing the issuance of such WWAs.
URGENT - WEATHER MESSAGE National Weather Service Missoula MT 237 PM MST Sun Mar 3 2019 MTZ002-003-007-043-041800- /O.NEW.KMSO.EC.W.0001.190304T0300Z-190304T1800Z/ West Glacier Region-Flathead/Mission Valleys- Butte/Blackfoot Region-Potomac/Seeley Lake Region- 237 PM MST Sun Mar 3 2019 ...EXTREME COLD WARNING IN EFFECT FROM 8 PM THIS EVENING TO 11 AM MST MONDAY... The National Weather Service in Missoula has issued an Extreme Cold Warning, which is in effect from 8 PM this evening to 11 AM MST Monday. * TEMPERATURES...15 to 30 below zero, with local areas down to 40 below zero. * TIMING...Late this evening through mid morning Monday. * IMPACTS...Local power outages and broken pipes are possible due to the extreme cold. PRECAUTIONARY/PREPAREDNESS ACTIONS... An Extreme Cold Warning means that dangerously low temperatures are expected for a prolonged period of time. Frostbite and hypothermia are likely if exposed to these temperatures, so make sure a hat, facemask, and heavy gloves or mittens are available. && $$
- Severe weather terminology (United States)
- Excessive heat warning - the polar opposite of an Extreme cold warning
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