SIGMET information

SIGMET information (significant meteorological information)

Information issued by a meteorological watch office concerning the occurrence or expected occurrence of specified en-route weather phenomena which may affect the safety of aircraft operations (ICAO). Information is issued with respect to one or more of the following phenomena: active thunderstorms, tropical revolving storms, severe line squall, heavy hail, severe turbulence, severe icing, marked mountain waves, or widespread sandstorms or dust storms.