AIRMETs and SIGMETs and the inflight advisories buried in your weather briefing that you need to stop skipping over

AIRMETs and SIGMETs are the inflight weather advisories that cover the miles of sky between your departure and destination — the gaps that no METAR or TAF addresses. While METARs report current conditions at a single airport and TAFs forecast conditions at that same airport, AIRMETs and SIGMETs paint the big picture across entire regions of airspace. If you’re not reading them, you’re planning your flight with blinders on.

What’s the Difference Between METARs, TAFs, and AIRMETs?

A METAR tells you what the weather is doing right now at one airport. A TAF tells you what it’s probably going to do over the next day or so at that same airport. But between your departure and your destination, there are miles of sky that no METAR covers.

That’s where AIRMETs and SIGMETs live. They describe hazardous weather conditions across broad geographic areas, giving you the regional picture that point-based reports can’t provide.

What Are the Three Types of AIRMETs?

AIRMET stands for Airmen’s Meteorological Information. Despite the name, these advisories apply to all pilots — VFR, IFR, student, and private alike. There are three types, each identified by a code name:

AIRMET Sierra — IFR Conditions and Mountain Obscuration. This means ceilings below 1,000 feet or visibility below 3 miles, or mountains obscured by clouds and fog. For VFR pilots, this is critical. VFR flight into instrument meteorological conditions remains one of the leading causes of fatal general aviation accidents, according to the NTSB. An AIRMET Sierra on your route is the weather telling you that parts of your trip may not be VFR by the time you arrive.

AIRMET Tango — Turbulence. This covers moderate turbulence, sustained surface winds of 30 knots or more, or low-level wind shear. Moderate turbulence in a Cessna 172 feels dramatically different than in an airliner. In a training airplane, it means fighting the airplane instead of flying it — something you want to know about before launch.

AIRMET Zulu — Icing. This covers moderate icing and freezing levels. Most training airplanes are not certified for flight into known icing conditions. Period. Ice changes your wing shape, raises your stall speed, and increases the power needed to maintain altitude — all of it happening gradually until suddenly nothing works the way it should. The FAA has dedicated advisory circulars to this hazard for good reason.

A simple memory aid: S-T-Z = Sight, Tumble, Zap. You can’t see, you’re getting bounced, or you’re picking up ice.

What Are SIGMETs and Convective SIGMETs?

SIGMET stands for Significant Meteorological Information. If an AIRMET is a yellow caution flag, a SIGMET is a red one. SIGMETs are issued for weather dangerous to all aircraft, including airliners: severe icing, severe or extreme turbulence, dust storms and sandstorms reducing visibility below three miles, and volcanic ash.

Then there’s the Convective SIGMET — the one that should stop you in your tracks. These are issued for:

• Severe thunderstorms with surface winds greater than 50 knots
• Hail at the surface ¾ inch or greater
• Tornadoes
• Embedded thunderstorms
• Lines of thunderstorms
• Thunderstorm areas covering 40% or more of an area of at least 3,000 square miles

Convective SIGMETs are issued every hour for the eastern, central, and western United States. A Convective SIGMET anywhere near your route demands serious reconsideration.

One common misconception: you don’t have to fly through a thunderstorm for it to affect you. A Convective SIGMET 50 miles off your route can still throw turbulence and wind shear your direction. Thunderstorms do not stay in their lane.

How Do You Find and Read AIRMETs and SIGMETs?

In apps like ForeFlight or Garmin Pilot, AIRMETs and SIGMETs appear as shaded regions on the graphical weather overlay — typically yellow or blue for AIRMETs, red for SIGMETs. If your route passes through a shaded zone, dig into the text.

In a standard text briefing (through 1-800-WX-BRIEF or text products directly), advisories follow a consistent format:

1. Advisory type (AIRMET Sierra, Tango, Zulu, or SIGMET)
2. Area described by VOR identifiers or geographic boundaries
3. Valid time
4. Hazard
5. Expected conditions

Here’s a real-world example. You’re planning a VFR cross-country from Nashville to Atlanta and your briefing includes:

AIRMET Tango Update 2, issued 1400Z. From Bowling Green to Chattanooga to Rome to Bowling Green. Moderate turbulence below 8,000 feet. Conditions continuing through 2000Z. Turbulence due to strong low-level winds.

This tells you that right along your route, moderate turbulence exists below 8,000 feet until 2000Z. If you’re planning to cruise at 5,500 feet, you’re flying through the middle of it. That doesn’t automatically mean you can’t go — but it means checking winds aloft at different altitudes, asking flight service for pilot reports along the route, considering an altitude adjustment, or delaying a few hours to see if conditions improve.

How Long Are These Advisories Valid?

These products update frequently, which matters for flight planning:

• AIRMETs are valid for 6 hours
• SIGMETs are valid for 4 hours
• Convective SIGMETs are valid for 2 hours

A briefing pulled at 8:00 AM may not reflect noon conditions. If your flight is more than a couple of hours away, check again before departure. In the air, listen to HIWAS (Hazardous Inflight Weather Advisory Service) on the nearest VOR frequency, or ask flight following for updates.

Why Do AIRMETs and SIGMETs Matter for Your Checkride?

The Airman Certification Standards (ACS) for the Private Pilot checkride specifically list weather information as a task area. The examiner expects you to obtain and interpret weather data for a proposed flight. That means you cannot point at METARs and TAFs and call it done.

You need to address AIRMETs and SIGMETs along the route, explain what they mean, and describe how they affect your go/no-go decision. An examiner who spots an AIRMET Sierra along the first half of your planned route will ask you about it.

A Practical Decision-Making Scenario

It’s Saturday morning. METARs along your route show clear skies and 10 miles visibility. TAFs look great. But there’s an AIRMET Zulu for moderate icing above 6,000 feet, the freezing level is at 5,800 feet, and your planned cruise altitude is 7,500 feet in a Cessna 172 with no de-ice equipment.

Your options:

• Climb above it? Unlikely — a non-turbocharged single struggles above 10,000 feet, and the icing may extend higher.
• Fly lower, below the freezing level? Possible, but check terrain and obstacles on the sectional, and recalculate fuel burn at a lower altitude in denser air.
• Wait it out? Check the AIRMET’s valid time. If the freezing level is forecast to climb above your cruise altitude by early afternoon, a delay of a few hours may solve the problem entirely.

That’s aeronautical decision making (ADM) in action — and it all starts with reading an AIRMET instead of scrolling past it.

A Better Briefing Habit to Start Now

Every time you pull a weather briefing, scan for AIRMETs and SIGMETs first, before looking at anything else. Start with the big picture: are there significant weather advisories affecting your route?

If the METARs look fine but an AIRMET Tango covers your entire route with moderate turbulence, the METARs aren’t telling the full story. If TAFs call for VFR but an AIRMET Sierra is moving in from the west, you need to think about timing.

Key Takeaways

• AIRMETs cover hazards between airports that METARs and TAFs miss — IFR conditions (Sierra), turbulence (Tango), and icing (Zulu)
• SIGMETs indicate weather dangerous to all aircraft, including airliners; Convective SIGMETs cover severe thunderstorms and should prompt serious go/no-go evaluation
• Always scan for AIRMETs and SIGMETs first when reviewing a weather briefing — they frame everything else
• Check validity times (6 hours for AIRMETs, 4 for SIGMETs, 2 for Convective SIGMETs) and re-brief if your flight is hours away
• Your checkride examiner will ask about advisories along your route — know how to find, read, and apply them to your decision

References: FAA Aviation Weather Services Advisory Circular (AC 00-45), Airman Certification Standards for Private Pilot.