A METAR is the routine weather observation an airport publishes for itself, in a format standardised worldwide by the WMO and ICAO. It looks like a password. It is actually a fixed sequence of groups, and once you know the order it reads left to right like a sentence.
Here is a real one, from Lucknow:
VILK 201130Z 08005KT 5000 BR FEW020 SCT025 32/28 Q1000 NOSIG| Group | Means |
|---|---|
| VILK | The station. A four-letter ICAO code — Chaudhary Charan Singh International Airport, Lucknow. Not the city: the airport. |
| 201130Z | Day 20 of the month, 11:30 UTC. The Z is Zulu, meaning UTC. Every METAR in the world is timestamped this way, never in local time. |
| 08005KT | Wind from 080° (east) at 5 knots. Direction first, three digits, then speed. VRB means variable, and a G — as in 08015G25KT — means gusting. |
| 5000 | Visibility, 5,000 metres. Most of the world reports metres; the US reports statute miles instead, written 10SM. |
| BR | Present weather: mist. These are two-letter codes — RA rain, SN snow, FG fog, HZ haze, TS thunderstorm — sometimes with an intensity prefix (- light, + heavy). |
| FEW020 | Few clouds at 2,000 feet. Cloud height is in hundreds of feet, so 020 is 2,000. |
| SCT025 | Scattered cloud at 2,500 feet. Coverage runs FEW → SCT → BKN (broken) → OVC (overcast). CAVOK or CLR means nothing worth reporting. |
| 32/28 | Temperature 32°C, dew point 28°C. Whole degrees, separated by a slash. A leading M means minus: M05/M10 is −5°C and −10°C. |
| Q1000 | Pressure, 1000 hPa, at mean sea level. The US writes it in inches of mercury instead: A3005 means 30.05 inHg. |
| NOSIG | No significant change expected in the next two hours. |
The temperature group in the body of a METAR is rounded to a whole degree Celsius. That is the standard, everywhere. So Lucknow's 32/28 genuinely means "32°C", not 32.4 or 31.6 — the finer number was never published.
United States stations add a remarks section that does carry the finer figure:
KSFO 201356Z 28007KT 10SM CLR 13/11 A3005 RMK AO2 SLP176 T01280106Everything after RMK is remarks. The group that matters here is T01280106:
T — this is the precise temperature group0 128 — sign 0 (positive), then 128 tenths of a degree: 12.8°C0 106 — sign 0, 106 tenths: dew point 10.6°CA sign digit of 1 means negative, so T10171034 would be −1.7°C with a dew point of −3.4°C.
The same airport can appear to report at two different precisions depending on which part of the line you read, and two stations in different countries are not measuring to the same resolution. San Francisco publishes tenths. Lucknow, Wellington, Paris and Shanghai publish whole degrees. Any Fahrenheit figure you see for those four is a conversion of a whole Celsius number, which is why they land on values like 89.6°F (exactly 32°C) rather than something in between.
A METAR only ever describes what was measured at that airport at that minute. The forecast equivalent is a TAF (Terminal Aerodrome Forecast), which is a different message with a different format. Nothing in a METAR predicts anything — NOSIG and the TEMPO/BECMG groups are the closest it gets, and they are short-range trend notes, not forecasts.
Airports publish a routine METAR on a fixed schedule — usually once or twice an hour, at the same minutes past the hour every time. Between those, a station can issue a SPECI: an unscheduled special report, triggered when conditions change sharply.
A SPECI is a real observation, but it is not part of the hourly record. That distinction turns out to matter a great deal for how this site stores readings, which is covered in how we process the data.