Red Flag Warning - Wikipedia

Term used by meteorologists indicating conditions favorable for wildfire development For other uses, see Red flag.

A red flag warning is a forecast warning issued by the National Weather Service (NWS) in the United States to inform the public, firefighters, and land management agencies that conditions are ideal for wildfire combustion, and rapid spread.[1][2] It is a form of emergency alert.

Criteria

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Red flag warnings are associated with drought conditions, very low humidity, high or erratic winds, and the possibility of lightning.

The weather criteria for fire weather watches and red flag warnings vary with each Weather Service office’s warning area based on the local vegetation type, topography, and distance from major water sources. They usually include the daily vegetation moisture content calculations, expected afternoon high temperature, afternoon minimum relative humidity, and daytime wind speed.

Responses

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Firefighting agencies often respond to such a warning by altering their staffing and equipment resources dramatically. To the public, the warning means high fire danger with increased probability of a quickly spreading vegetation fire in the area within 24 hours.

Outdoor burning bans may also be proclaimed by local law and fire agencies based on red flag warnings, for both the general public and land management officials. A fire weather warning gives extra guidance to land management officials to refrain from controlled burns.

Related warnings

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In October 2019, the National Weather Service introduced a variant to denote even more dangerous conditions: extreme red flag warning. Analogous to the particularly dangerous situation (PDS) wording on a high-end severe weather warning or watch, this means that conditions for fire growth and behavior are extremely dangerous due to a combination of strong winds, very low humidity, long duration, and very dry fuels. It was used for the first time on October 29, 2019.[3]

A related but less imminent forecast may include a fire weather watch, which is issued to alert fire and land management agencies to the possibility that Red Flag conditions may exist beyond the first forecast period (12 hours). The watch is issued generally 12 to 48 hours in advance of the expected conditions, but can be issued up to 72 hours in advance if the NWS agency is reasonably confident. The term “Fire Weather Watch” is headlined in the routine forecast and issued as a product, similar to the other primary fire warning terms.[4] That watch then remains in effect until it expires, is canceled, or upgraded to a red flag warning.

See also

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• Australian Fire Danger Rating System (Australia)
• Severe weather terminology (Canada)

References

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1. ^ "Red Flag Warning". National Weather Service. 2015-03-05. Retrieved 2018-05-02.
2. ^ Services, Florida Department of Agriculture and Consumer. "Florida Department of Agriculture & Consumer Services". www.fdacs.gov. Retrieved 2025-04-22.
3. ^ "'Extreme' warning issued ahead of hurricane-force Santa Ana winds, the strongest since 2007". Los Angeles Times. 2019-10-29.
4. ^ "Three Wildfire Terms You Should Know". www.cleanairresources.com. 2019-02-24. Retrieved 2019-03-07.

External links

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• Fire weather forecasts (Storm Prediction Center)

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Winterweather	Advisories Winter weather advisory Winter storm Watch Warning Blizzard/blowing snow Blowing snow advisory Blizzard watch Blizzard warning Heavy snow Warning Lake-effect snow Advisory Watch Warning Snow squall Warning Ice Freezing rain advisory Ice storm warning Avalanche Warning Watch Advisory
Tropicalcyclones	Tropical storms Watch Warning Hurricanes Watch Warning Typhoons Watch Warning Cyclones Watch Warning Storm surge Watch Warning Hurricane local statement Tropical storm local statement Tropical depression local statement
Flood	Flood Watch Warning Advisory Flash flood Watch PDS watch Warning Emergency Coastal flood Advisory Watch Warning Statement Lakeshore flood Warning Advisory Watch Statement River flood Advisory Watch Warning Urban and small stream flood Advisory
Apparenttemperature	Heat index Heat advisory Extreme heat watch Extreme heat warning Extreme cold Cold Weather Advisory Extreme Cold Watch Extreme Cold Warning PDS warning Freeze Watch Warning Hard freeze warning Frost advisory Hard freeze watch
Maritimeandcoastalweather	Marine winds Small craft advisory Brisk wind advisory Lake wind advisory Gale Watch Warning Storm Watch Warning Hurricane-force wind Warning Watch Hazardous seas Watch Warning Freezing spray Freezing spray advisory Heavy freezing spray watch Heavy freezing spray warning Marine weather statement Rip current statement Beach hazards statement
High surf	High surf advisory High surf warning High surf watch
Wind	Advisory-force winds Wind advisory Gale-force winds High wind watch High wind warning Major hurricane-force winds Extreme wind warning
Airborneparticulates	Dust/sand Blowing dust advisory Blowing dust warning Dust advisory Dust storm warning Fog/Smoke Dense fog advisory Dense smoke advisory Ash Ashfall advisory Ashfall warning Air pollution Air stagnation advisory Air quality alert
Fire	Red flag warning Fire warning Evacuation immediate Fire weather watch
Aviation	SIGMET Volcanic ash advisory
Weather scalesused by NWS	Beaufort (wind) Enhanced Fujita (tornadoes) Saffir–Simpson scale (tropical cyclones)
Other	Special weather statement Severe weather statement Hazardous weather outlook
Tsunami	Watch Warning Advisory