An extreme cold warning is a severe weather alert issued by Canada's Environment and Climate Change Canada (ECCC) and the U.S. National Weather Service (NWS) to inform the public about dangerously cold temperatures or wind chills. In April 2014, ECCC replaced its "wind chill warning" with this system, which triggers alerts when temperatures or wind chills drop to specific regional thresholds—ranging from -30°C to -55°C—and are expected to last for at least two hours. The NWS officially adopted the term on October 1, 2024, replacing its "wind chill warning" as part of its "Hazard Simplification initiative" to streamline cold weather messaging. This wasn't the NWS's first use of the term, as it was tested experimentally in 2011 in states like North Dakota and Minnesota, but was discontinued after that season. Under the new NWS framework, an "extreme cold watch" serves as the step below the warning, consolidating previous wind chill and extreme cold products into a single, clearer warning scheme for better public decision support.