Hurricane force wind warning

A hurricane force wind warning is a warning issued by the National Weather Service of the United States when sustained winds or frequent gusts of 64 knots (118 km/h, 74 mph) or greater are either being observed or are predicted to occur. The winds must not be directly associated with a tropical cyclone, or a hurricane warning will be issued. If winds are lighter than 64 knots, a storm warning or gale warning will be issued. The hurricane force wind warning is only used to warn of the possibility of wind which reaches hurricane-level severity, but lacks direct connection with a hurricane system. The hurricane force wind can either signal sustained winds of 64 knots, or gusts of 64 knots lasting for two or more hours.

In US maritime warning flag systems, two red square flags with a black square taking up the middle ninth of each flag is used to indicate a hurricane force wind warning (the use of one such flag denotes a storm warning or a tropical storm warning). The flags used to denote hurricane force winds are also used to warn of incoming hurricanes.