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   You are at: NWS Home » SRH Home » WFO Tallahassee Home » What are Red Flag Warnings?

What are Red Flag Warnings & Fire Weather Watches?
The National Weather Service (NWS) issues Red Flag Warnings & Fire Weather Watches to alert land management agencies of the onset, or possible onset, of critical weather and fuel moisture conditions that could lead to rapid or dramatic increases in wildfire activity. This could be due to low relative humidity, strong winds, dry fuels, or any combination thereof. You may have noticed that the Watch/Warning/Advisory map on our homepage turns red or orange when a Red Flag Warning or Fire Weather Watch is issued. Each year, the NWS coordinates with each state to implement a State Operating Plan related to fire weather services. Red flag criteria are set in these plans and vary from state to state. NWS Tallahassee serves portions of three states, each with their own red flag criteria. These criteria are summarized in the table below.

FLORIDA
  • Relative humidity less than 35% for 4 or more consecutive hours, OR
  • Any occurrence of relative humidity less than 35% concurrent with 20-ft winds speeds of 15 mph or greater, OR
  • Any occurrence of a dispersion index of 75 or greater concurrent with a relative humidity less than 35%.
    • GEORGIA
  • 1 Nov. - 30 April: Relative humidity less than 25% for 4 or more consecutive hours, OR
    Any occurrence of relative humidity less than 25% concurrent with ASOS winds speeds of 20 mph or greater AND/OR frequent gusts to 25 mph or greater.
  • 1 May - 31 Oct.: Relative humidity less than 30% for at least 1 hour concurrent with sustained ASOS wind speeds greater than or equal to 20 mph, AND/OR frequent gusts to 25 mph or greater.
    • ALABAMA
  • 1 Nov. - 30 April: Relative humidity less than 25% for 4 or more consecutive hours, OR
    Any occurrence of relative humidity less than 25% concurrent with 20-ft winds speeds of 20 mph or greater.
  • 1 May - 31 Oct.: Relative humidity less than 30% for at least 1 hour concurrent with sustained 20-ft wind speeds greater than or equal to 10 mph, AND
    The Keetch-Byrum Drought Index (KBDI) is greater than or equal to 500, OR, the Alabama Forestry Commission has issued a Fire Alert.

    • A red flag warning is issued when the above conditions are expected to be met within the next 24 hours. A fire weather watch is issued when the above conditions are expected to be met beyond 24 and out to 72 hours. Typically, these watches and warnings are issued at the same time the routine fire weather forecasts are issued, 7:30 AM and 3:30 PM EST.

    A glossary of fire weather terms is provided here for your reference.

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