Reading the Sky in Code: How to Decode a METAR

Few artifacts of aviation look more impenetrable to an outsider than a METAR. A typical example — KMIA 221753Z 09012KT 10SM FEW025 SCT250 30/23 A3001 — appears to be a typo until you know the grammar. Once you do, it reads like a sentence. METAR stands for Meteorological Aerodrome Report, the standard hourly observation issued by airports worldwide. The format is rigid by design, so a pilot in Miami and a controller in Munich parse it identically. The first block is the station identifier — here KMIA, Miami International. Next comes the observation time in Zulu (UTC): 221753Z means the 22nd day of the month at 1753 Zulu. Aviation runs on Zulu precisely so a global system never argues about time zones. Then the weather itself, always in the same order. 09012KT is wind: from 090 degrees true at 12 knots. 10SM is visibility: ten statute miles, effectively unlimited. The cloud groups follow in hundreds of feet above the field: FEW025 is a few clouds at 2,500 feet, SCT250 scattered at 25,000. Temperature and dewpoint come as 30/23 in Celsius — a spread that hints at humidity and the risk of fog as they converge. Finally A3001 is the altimeter setting, 30.01 inches of mercury, which a pilot dials into the altimeter so it reads true field elevation. Per 14 CFR §91.103, a pilot must review available weather before flight, and the METAR is the bedrock of that review. Crucially, it is an observation, not a forecast — a snapshot of what is, not what will be. That is the TAF's job. AeroLink renders every METAR with a visible age indicator because a weather report, however precise, is only as good as how recently it was taken.