Storm warning

At sea, a storm warning is a warning issued by the National Weather Service of the United States when winds between 48 knots (89 km/h, 55 mph) and 63 knots (117 km/h, 73 mph) are occurring or predicted to occur soon.

In US maritime warning flag systems, a red square flag with a black square taking up the middle ninth of the flag is used to indicate a storm warning (the use of two such flags denotes a hurricane force wind warning or a hurricane warning).

On land, the National Weather Service issues a 'high wind warning' (Specific Area Message Encoding code: HWW) for storm-force winds, which also encompasses the lesser gale-force and greater hurricane force winds.

Winds in excess of 115 MPH (100 kt) will always result in new issuance of an extreme wind warning shortly before their onset, typically right before the eyewall of a major hurricane makes landfall, but possibly as a substitute for a severe thunderstorm warning in an extreme derecho event.

The following is an example of a storm warning issued by the National Weather Service office in Seattle, Washington.