Plain English Meaning

Weather that is dangerous enough to threaten an aircraft in flight or during takeoff and landing. It is the kind of weather pilots need to plan around, avoid, or divert from rather than fly through.

Full Definition

Weather conditions that pose a significant risk to the safety of flight, including thunderstorms, icing, turbulence, low ceilings and visibility, wind shear, and volcanic ash. The FAA disseminates information about these conditions through specific products such as SIGMETs, , , , and .