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What exactly does a Red Flag Warning mean? - KVOA | KVOA.com | Tucson, Arizona

What exactly does a Red Flag Warning mean?

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Courtesy: Keith Carender Courtesy: Keith Carender

TUCSON - For desert dwellers, Red Flag Warnings are synonymous with a high fire danger.

Seems basic, but for meteorologists at the National Weather Service, there's certain criteria that goes into a Red Flag Warning. In order for a Red Flag Warning to be issued, these three conditions need to be met for at least three hours.

- Sustained winds of at least 20 MPH

- Relative humidity values less than or equal to 15%

- Dry vegetation

If there are indications of a high fire danger, the National Weather Service may first issue a Fire Weather Watch. This means red flag conditions may occur in the next 24-72 hours. 

If the three fire weather criteria listed above are likely to develop within 24 hours, Red Flag Warnings are then issued by the National Weather Service.

How's this for an interesting weather fact? The "red flag" label originates from the US Forest Service, when they would raise a red flag to call attention to the day's high fire danger.

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