A winter storm warning is a hazardous weather alert issued by the National Weather Service (NWS) in the United States and Environment and Climate Change Canada (ECCC) to notify the public that severe winter weather is expected within 36 hours. The criteria typically require snow accumulations of 4–7 inches (10–18 cm), or 3 inches with significant ice, but this threshold drops to as low as 1 inch (2.5 cm) in the Southern US, where winter storms are rarer and more impactful. The warning is distinct from a blizzard warning, which is issued when winds exceed 35 mph accompany heavy snowfall, while significant ice alone triggers an ice storm warning instead. Beginning with the 2008–09 winter season, the NWS consolidated specific warnings (like heavy snow and sleet) into distinct variants of the Winter Storm Warning product, such as "heavy wet snow" and "snow and ice," with heavy lake-effect snow added in the 2017–18 season. These warnings can also incorporate verbiage for wind chill warnings or wind advisories to cover additional hazards like dangerous cold or strong gusts.