An AIRMET (AIRman's METeorological Information) advises of weather that may be hazardous, other than convective activity, to single engine, other light aircraft, and Visual Flight Rule (VFR) pilots. However, operators of large aircraft may also be concerned with these phenomena. The items covered are:

AIRMET Sierra (IFR):

Red polygon regions of ceilings less than 1000 feet and/or visibility less than 3 miles affecting over 50% of the area at one time, labeled IFR

Yellow polygon regions of extensive mountain obscuration, labeled MTOS

AIRMET Tango (Turbulence):

Light blue polygon regions of moderate turbulence, labeled

Sustained surface winds of 30 knots or more at the surface

AIRMET Zulu (Icing):

Light green polygon regions of moderate icing, labeled

Freezing levels

AIRMETs are routinely issued for 6 hour periods beginning at 0145 UTC during Central Daylight Time and at 0245 UTC during Central Standard Time. AIRMETs are also amended as necessary due to changing weather conditions or issuance/cancelation of a SIGMET.