Definition
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. Under ICAO standards, SIGMETs cover hazards such as thunderstorms, severe turbulence, severe icing, volcanic ash, tropical cyclones, and dust or sandstorms.
Plain English
An official weather warning issued to pilots about dangerous weather along their route that could threaten flight safety.
Context Anchor
Seen in aviation weather briefings, flight planning systems, and international weather products before or during a flight.
Derivation
SIGMET is short for Significant Meteorological Information. The word 'significant' here carries its strict meaning: important enough to affect flight safety, not just notable.
Why Pilots Care
Allows pilots to reroute, delay, or cancel flights to avoid hazardous weather that could lead to loss of control or structural damage.
Intuition Check
Do not read “information” here as just general background weather. SIGMET Information [ICAO] is a formal warning about specific hazardous weather that may affect flight safety.
Example Sentence 1
During the preflight briefing, the crew noted a SIGMET for severe turbulence along their planned route and chose an alternate altitude.
Example Sentence 2
While en route the crew received an updated SIGMET Information for icing conditions and requested a lower altitude from ATC.