METAR

thumb|upright|A METAR processing and transmitting unit installed at [[Pittsburgh-Butler Regional Airport, Pennsylvania, U.S.]]

METAR<!--Don't add "METeorological Actual Report" or any other meaning here. See the "Report names" section below."--> is a format for reporting weather information. A METAR weather report is predominantly used by aircraft pilots, and by meteorologists, who use aggregated METAR information to assist in weather forecasting.

Raw METAR is highly standardized through the International Civil Aviation Organization (ICAO), which enables it to be understood throughout most of the world.

Report names

In its publication the Aeronautical Information Manual (AIM), the United States Federal Aviation Administration (FAA) describes the report as aviation routine weather report, while the international authority for the code form, the World Meteorological Organization (WMO), describes it as the aerodrome routine meteorological report. The National Oceanic and Atmospheric Administration (part of the United States Department of Commerce) and the United Kingdom's Met Office both employ the definition used by the FAA. METAR is also known as Meteorological Terminal Aviation Routine Weather Report or Meteorological Aerodrome Report.

Frequencies and types

METARs typically come from airports or other permanent weather observation stations. Reports are generated once an hour or half-hour at most stations, but if conditions change significantly at a staffed location, a report known as a special (SPECI) may be issued.