Garmin GDU 37X Pilot's Manual page 150

Hazard Avoidance
AIRMETS
An AIRMET (AIRmen's METeorological Information) can be especially helpful for
pilots of light aircraft that have limited flight capability or instrumentation. An AIRMET
must affect or be forecast to affect an area of at least 3,000 square miles at any one
time. AIRMETs are routinely issued for six-hour periods and are amended as necessary
due to changing weather conditions. AIRMETs are displayed as colored, dashed lines.
SIGMETS
A SIGMET (SIGnificant METeorological Information) advises of weather that is
potentially hazardous to all aircraft. In the contiguous United States, the following
items are covered: severe icing, severe or extreme turbulence, volcanic ash, dust storms,
and sandstorms that lower visibility to less than three statute miles.
A Convective SIGMET is issued for the following conditions: thunderstorms, isolated
severe thunderstorms, embedded thunderstorms, hail at the surface, and tornadoes.
A SIGMET is widespread and must affect or be forecast to affect an area of at least
3,000 square miles. SIGMETs are displayed as a yellow-dashed line.
AIRMET/SIGMET Legend
132
METAR Legend
Garmin GDU 37X Pilot's Guide
™
METAR Selected With Map
Pointer
AIRMET Selected With Map
Pointer
190-01054-00 Rev. E