SIGMET (Significant Meteorological Information)

A SIGMET (Significant Meteorological Information) is a weather advisory issued by a Meteorological Watch Office (MWO) to advise pilots of the occurrence or expected occurrence of specified en route weather phenomena that may affect the safety of all aircraft operations. SIGMETs are the highest-priority weather advisories in aviation.

SIGMET Criteria

  • Severe turbulence (not associated with thunderstorms)
  • Severe icing (not associated with thunderstorms)
  • Severe mountain wave turbulence
  • Thunderstorms (obscuring flight visibility; widespread; embedded)
  • Tropical cyclones
  • Dust storms or sandstorms raising dust to 6,000 ft or more
  • Volcanic ash
  • Radioactive cloud

SIGMET vs. AIRMET

SIGMETs are for severe phenomena affecting all aircraft. AIRMETs cover conditions significant to light aircraft (moderate icing, moderate turbulence, low ceilings). A SIGMET requires serious respect regardless of aircraft type — encountering severe icing or severe turbulence can destroy any aircraft.

How to Find SIGMETs

SIGMETs are available through the FIC (1-866-WXBRIEF), NAVCANatm.ca, and aviation weather apps. They must be checked as part of every pre-flight weather briefing. In flight, request SIGMET information from FIC on the appropriate frequency.

On the TC Written Exam

SIGMET criteria and the distinction from AIRMET are tested on both PPL and CPL exams. Know: SIGMETs are for severe or extreme conditions affecting all aircraft; they must be checked pre-flight; they take priority over other weather products.

Related Terms

See also: AIRMET, Icing, Clear Air Turbulence, Thunderstorm.