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What is a Red Flag Warning?

Acccording to the National Weather Service web page:

Red flag warning is a term used by fire-weather forecasters to call attention to limited weather conditions of particular importance that may result in extreme burning conditions. It is issued when it is an on-going event or the fire weather forecaster has a high degree of confidence that Red Flag criteria will occur within 24 hours of issuance.

Red Flag criteria occurs whenever a geographical area has been in a dry spell for a week or two, or for a shorter period , if before spring green-up or after fall color, and the National Fire Danger Rating System (NFDRS) is high to extreme and the following forecast weather parameters are forecasted to be met:

    1) a sustained wind average 15 mph or greater
    2) relative humidity less than or equal to 25 percent and
    3) a temperature of greater than 75 degrees F.

In some states, dry lightning and unstable air are criteria. A Fire Weather Watch may be issued prior to the Red Flag Warning.

Here’s another interesting explanation from the NWS:

Sky Condition
    Used in a forecast to describes the predominant/average sky condition based upon octants (eighths) of the sky covered by opaque (not transparent) clouds.

    Sky Condition                                    Cloud Coverage
    Clear / Sunny                                             0/8
    Mostly Clear / Mostly Sunny                     1/8 to 2/8
    Partly Cloudy / Partly Sunny                     3/8 to 4/8
    Mostly Cloudy / Considerable Cloudiness    5/8 to 7/8
    Cloudy                                                         8/8
    Fair (mainly for night)                        Less than 4/10 opaque clouds, no precipitation,                                                               no extremes of visibility/temperature/wind

Check out our weather glossary for more weather terms.