How long does a SIGMET remain valid?

A SIGMET, or significant meteorological information, is issued to warn pilots of potentially hazardous weather conditions that can impact flight safety, such as thunderstorms, turbulence, icing, or volcanic ash. The validity of a SIGMET is typically established for a duration of four hours.

When a SIGMET is issued, it is meant to provide timely updates to pilots about weather conditions that may change relatively quickly. After four hours, the SIGMET can either be updated, canceled, or replaced with new information if the conditions persist. The four-hour validity period allows for efficient and relevant dissemination of critical weather information, ensuring that pilots are aware of changing conditions as they plan and conduct their flights.

This is the protocol set by the International Civil Aviation Organization (ICAO) to ensure safety in air traffic, as weather can have significant implications for navigation and operational procedures. Therefore, it is essential for pilots and flight crews to remain vigilant and to check the latest SIGMETs during their flight planning and operations for the most current weather information.