Severe weather terminology (United States)

This article describes severe weather terminology used by the National Weather Service (NWS) in the United States, a government agency operating within the Department of Commerce as an arm of the National Oceanic and Atmospheric Administration (NOAA).

The NWS provides weather forecasts, hazardous weather alerts, and other weather-related products for the general public and special interests through a collection of national and regional guidance centers (including the Storm Prediction Center, the National Hurricane Center and the Aviation Weather Center), and 122 local Weather Forecast Offices (WFO). Each Weather Forecast Office is assigned a designated geographic area of responsibility—also known as a county warning area—that are split into numerous forecast zones (encompassing part or all of one county or equivalent thereof) for issuing forecasts and hazardous weather products.

The article primarily defines precise meanings and associated criteria for nearly all weather warnings, watches, advisories, statements, and other products not associated with hazardous weather issued by the NWS and its sub-organizations (some of which may be specific to certain cities or regions). Related weather scales and general weather terms used by the agency are also addressed.

Definitions of severe weather alerts

The NWS divides severe weather alerts into several types of hazardous/hydrologic events:

Severe local storms – Short-fused, small-scale hazardous weather or hydrologic events produced by thunderstorms (including large hail, damaging winds, tornadoes, and flash floods).

Winter storms – Weather hazards associated with freezing or frozen precipitation (freezing rain, sleet, and/or snow), or combined effects of winter precipitation and strong winds.

Fire weather – Weather conditions that contribute to an increased risk and help cause the spread of wildfires.

Flooding – Hazardous hydrological events resulting in temporary inundation of land areas not normally covered by water, often caused by excessive rainfall.

Coastal/lakeshore hazards – Hydrological hazards that may affect property, marine or leisure activities in areas near ocean and lake waters including high surf and coastal or lakeshore flooding, as well as rip currents.