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, Convective SIGMETs, AIRMETs, Center Weather Advisories, and PIREPs.
Plain English
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.
Context Anchor
A pilot meets this term during preflight weather planning, go/no-go decisions, and in-flight decisions about whether to continue, divert, or avoid an area.
Derivation
“Hazardous” comes from “hazard,” a word that came to mean danger or risk. That helps in aviation because hazardous weather is not just “bad-looking” weather; it is weather that adds real risk to the flight.
Why Pilots Care
Failing to recognize and avoid hazardous weather is a leading cause of weather-related accidents; pilots must treat it as a go/no-go decision factor.
Grounding Statement
If the weather ahead would force the pilot into poor visibility, strong bumps, ice, or storm activity, treat it as hazardous until there is a safe plan to avoid it.
Intuition Check
Hazardous weather does not mean only severe storms. In aviation, ordinary-looking weather can be hazardous if it creates unsafe conditions for that pilot, aircraft, route, or phase of flight.
Example Sentence 1
During the preflight briefing, the pilot noted hazardous weather along the route in the form of a line of thunderstorms and chose to delay departure by two hours.
Example Sentence 2
After encountering unexpected turbulence and icing, the crew recognized they had entered hazardous weather and requested an immediate diversion.