National Weather Service Weather Forecast Office

An AIRMET (AIRman's METeorological Information) advises of weather that maybe 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):

Ceilings less than 1000 feet and/or visibility less than 3 miles affecting over 50% of the area at one time.

Extensive mountain obscuration




AIRMET Tango (Turbulence):

Moderate turbulence

Sustained surface winds of 30 knots or more at the surface




AIRMET Zulu (Icing):

Moderate icing

Freezing levels

These AIRMET items are considered to be widespread because they must be affecting or be forecast to affect an area of at least 3000 square miles at any one time. However, if the total area to be affected during the forecast period is very large, it could be that only a small portion of this total area would be affected at any one time.

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.