Definition: Red Flag Warnings are issued by the National Weather Service when conditions are conducive to the formation of wildfires. Dry conditions combined with high winds and low humidity are the hallmarks of weather conducive to producing large wildfires. In areas where dry thunderstorms are common, the hazards are considered critical and imminent.
The three basic ingredients for a wildfire are strong winds, low relative humidity, and high temperatures. In addition, persistently dry vegetation provides an easy fuel source for the fires. If the conditions are either not currently occurring or about to occur, a Fire Weather Watch is issued. Red Flag Warnings mean there is an expectation for explosive fire growth potential.