How to Interpret AIRMETs and SIGMETs
AIRMETs and SIGMETs are not decorations on a weather map. They are organized warnings for hazards that can affect entire regions: IFR, mountain obscuration, turbulence, icing, thunderstorms, dust storms, volcanic ash, and more. The key is knowing what each product means for your aircraft, your route, and your legal or personal minimums.
Prerequisites
- → Route of flight and planned altitude
- → METAR, TAF, and radar review
- → Aircraft equipment and icing limitations
- → Personal or company weather minimums
Step-by-Step
- 1
Start with the product type
AIRMETs cover widespread but generally less extreme hazards. SIGMETs cover significant hazards. Convective SIGMETs cover thunderstorms and severe convective activity.
- 2
Know the three AIRMET families
Sierra covers IFR and mountain obscuration. Tango covers turbulence, strong surface winds, and low-level wind shear. Zulu covers icing and freezing levels.
- 3
Check the valid time and update cycle
Do not use an expired advisory. Weather hazard products are time-bounded, and an old AIRMET can be less useful than a fresh PIREP or radar trend.
- 4
Map the polygon against your route
The question is not whether an advisory exists somewhere in the state. The question is whether your route, altitude, and time cross the affected area.
- 5
Translate hazard into aircraft-specific risk
Moderate icing means something very different in a non-FIKI piston single than in a turbine aircraft with certified anti-ice equipment. Apply the advisory to your actual aircraft.
- 6
Use SIGMETs as strategic avoid areas
If a SIGMET or convective SIGMET affects your route, plan a route around it, delay, or cancel. Do not plan to simply thread through it because the line looks narrow.
- 7
Cross-check with real observations
AIRMETs and SIGMETs should be compared with METARs, TAFs, radar, satellite, and PIREPs. The advisory tells you where the risk is organized; observations tell you how it is behaving now.
Common Mistakes
- × Seeing an AIRMET and canceling automatically without checking route and altitude
- × Seeing no advisory and assuming there is no hazard
- × Treating a SIGMET like a normal forecast note
- × Ignoring freezing level when reading AIRMET Zulu
- × Failing to update the briefing before departure
Pro Tips
- ★ For VFR pilots, AIRMET Sierra is often the most important one to respect
- ★ For light GA, AIRMET Zulu can be a hard stop if clouds and freezing temperatures overlap your route
- ★ For mountain routes, combine AIRMET Tango with winds aloft and PIREPs
- ★ If a convective SIGMET intersects your route, build a new route instead of negotiating with thunderstorms
Conclusion
AIRMETs and SIGMETs are decision tools. Read the hazard type, time, altitude, and geography, then translate that into a clear plan: go, delay, reroute, change altitude, or cancel.
FAQ
What is AIRMET Sierra?
AIRMET Sierra covers IFR conditions and mountain obscuration over a broad area.
What is AIRMET Tango?
AIRMET Tango covers turbulence, sustained strong surface winds, and low-level wind shear.
What is AIRMET Zulu?
AIRMET Zulu covers icing and freezing-level information.
Is a SIGMET more serious than an AIRMET?
Yes. A SIGMET describes significant weather hazards that may be dangerous to aircraft and should drive stronger avoidance planning.