A METAR is an observation of current surface weather reported in a standard format.
METARs are issued on a regularly scheduled basis unless significant weather changes have occurred. A special METAR (SPECI) can be issued at any time between routine METAR reports. A typical METAR report contains the following information in sequential order: type of report, station identifier, date and time of report, modifier, wind, visibility, weather, sky condition, temperature and dew point, altimeter setting, Zulu time, remarks.
Example: METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR
Explanation: Routine METAR for Gregg County Airport for the 16th day of the month at 1753Z automated source. Winds are 140 at 21 knots gusting to 26. Visibility is 3⁄4 statute mile. Thunderstorms with heavy rain and mist. Ceiling is broken at 800 feet, overcast at 1,200 feet with cumulonimbus clouds. Temperature 18 °C and dew point 17 °C. Barometric pressure is 29.70Hg and the pressure is falling rapidly.
FAA AC 00-45H Aviation Weather Services pg. 3-1
FAA-H-8083-25B Pilot’s Handbook of Aeronautical Knowledge pg. 13-7