METAR vs TAF: What Each One Tells You
Learn what a METAR observes, what a TAF forecasts, how their schedules and coverage differ, and which one to trust at each stage of a preflight brief.
A METAR tells you what the weather at an airport is doing right now. A TAF tells you what it is expected to do over the next 24 to 30 hours. That is the whole difference in one line: a METAR is an observation, a TAF is a forecast. One is a measurement you can hold the atmosphere to; the other is a forecaster’s professional judgment about what comes next.
That distinction settles most “which one do I check” questions before they start. Deciding whether we can launch into the pattern in the next twenty minutes is METAR work. Deciding whether the ceiling at our destination will still be legal three hours from now is TAF work. A good brief uses both and pays close attention when they disagree. This post covers what each product contains, when it is issued, and where each one earns its keep. For how both fit into the full sequence, big picture down to runway numbers, see our complete preflight weather briefing guide.
What a METAR contains
A METAR (Aviation Routine Weather Report) is a snapshot of surface conditions at one reporting point, most often an automated ASOS or AWOS station, sometimes augmented by a human observer. A standard report carries the station identifier, observation time, wind, visibility, present weather, sky condition, temperature and dew point, altimeter setting, and remarks. Present weather is where fog and mist live, and the codes are worth knowing cold; which fog type you’re looking at, and when it will actually burn off, is its own subject.
Two issuance types exist. The routine METAR comes out hourly, with most stations observing in the last few minutes before the top of the hour. A SPECI is an unscheduled special report issued between the hourly ones whenever conditions change significantly: a thunderstorm begins, the ceiling drops through a decision-relevant value, the wind shifts. If you see SPECI in place of METAR, something at that field just moved.
Here is one read the way we would say it out loud. Lincoln, Nebraska, observed at 1754Z: wind from 180 at 12 knots gusting 18, visibility 10 statute miles, scattered clouds at 4,500 ft, a broken deck way up at 25,000 ft, temperature 31°C, dew point 17°C, altimeter 29.92. A gusty but comfortably VFR summer afternoon. The raw string behind that reading:
METAR KLNK 231754Z 18012G18KT 10SM SCT045 BKN250 31/17 A2992 RMK AO2 SLP122If a group in a raw report stops you, paste the whole line into our METAR decoder and read the plain-English version next to the code until the code stops needing translation.
What a TAF contains
A TAF (Terminal Aerodrome Forecast) is written by a human forecaster at a National Weather Service forecast office, and it covers a small area: conditions within 5 statute miles of the center of the airport’s runway complex. Not the practice area, not your route, not the field 15 NM away. Five miles.
Scheduled TAFs come out four times a day, with valid periods starting at 0000Z, 0600Z, 1200Z, and 1800Z; the forecast itself is transmitted 20 to 40 minutes early, which is why the example below carries a 1720Z stamp. Most are valid for 24 hours; a set of major hub airports get 30-hour TAFs. The valid period reads as two day/hour pairs, so 2318/2418 means from the 23rd at 1800Z through the 24th at 1800Z.
The body of a TAF is a base forecast followed by change groups, and the change groups are where the actual forecasting lives:
- FM (from): a rapid, lasting change. Everything after an FM group is a complete new forecast that replaces what came before it.
- TEMPO: temporary fluctuations expected to last less than an hour at a time and, in total, less than half the period given. The base conditions still apply between episodes.
- PROB30: about a 30 percent chance of the stated conditions, usually thunderstorms or heavy precipitation, during the window given. Low enough that the forecaster will not commit, high enough to plan fuel around.
- BECMG (becoming): a gradual change across the window. NWS forecasters do not use BECMG in US civil TAFs, but you will meet it in military and international ones.
Read one the same way, decoded first. Lincoln again, issued 1720Z on the 23rd, valid from 1800Z through 1800Z the next day: wind 180 at 12 knots, visibility better than 6 statute miles, 5,000 scattered. Between 2000Z and 2300Z, occasional light rain showers with visibility down to 6 miles and a broken ceiling at 4,000 ft. From 0300Z, wind eases to 200 at 8 and the sky clears. From 1500Z, wind 210 at 12 gusting 20 with a broken deck at 4,500 ft, and between 1500Z and 1800Z a 30 percent chance of a thunderstorm with rain, 4 miles visibility, and a 3,000-ft broken cumulonimbus ceiling. The raw forecast:
TAF KLNK 231720Z 2318/2418 18012KT P6SM SCT050
TEMPO 2320/2323 6SM -SHRA BKN040
FM240300 20008KT P6SM SKC
FM241500 21012G20KT P6SM BKN045
PROB30 2415/2418 4SM TSRA BKN030CBWorking through an unfamiliar TAF group by group is exactly what our TAF decoder is for; it splits the change groups apart so you can see which forecast owns which hours.
METAR vs TAF at a glance
| METAR | TAF | |
|---|---|---|
| What it is | Observation of current conditions | Forecast of expected conditions |
| Who makes it | Mostly automated sensors (ASOS/AWOS), some human-augmented | A human forecaster at an NWS office |
| Cadence | Hourly, plus SPECI on significant change | Four times daily (periods start 0000Z, 0600Z, 1200Z, 1800Z), plus amendments |
| Looks ahead | Zero; it is already history when you read it | 24 hours, 30 at some major hubs |
| Coverage | The station’s immediate vicinity | 5 SM around the airport’s runway complex |
| Best use | Go/stay decisions in the next hour; checking whether the forecast is verifying | Planning arrivals hours out, fuel and alternate decisions |
When to lean on which
For a local flight departing soon, the METAR carries the brief. Pull the last two or three hourly reports, not just the latest one, and read them as a trend: is the gust spread widening, is the dew point closing on the temperature, is the ceiling stepping down? A single METAR is a data point; three in a row is a story.
For a cross-country, the order reverses. The TAFs at our destination and alternate, valid at our ETA, drive the plan; the METARs along the route tell us whether that plan is surviving contact with the atmosphere. This is also where the regulations point at forecasts: the alternate-airport minimums in 14 CFR 91.169 are judged at your estimated time of arrival, and the only product that can speak for a time still hours away is a forecast.
The highest-value habit is comparing the two. Look at the TAF line that covers the current hour, then look at the METAR. If the observation is already worse than the forecast said it would be, treat the rest of that TAF with suspicion; the forecaster’s model of the day is failing early. If the observation is better, that is worth noting too, but forecasts tend to bust toward pessimism less often than we would like.
One boundary to keep sharp: neither product says anything about the en route segment. Icing, turbulence, IFR conditions, and convection between airports are the job of AIRMETs and SIGMETs, and a brief that stops at METAR plus TAF has a hundred-mile hole in the middle of it.
The gotchas
Most GA airports have no TAF. The NWS writes TAFs for 715 US airports as of its June 2025 site list. Thousands of fields report METARs; far fewer get a forecast. If your home field has an AWOS but no TAF, the nearest TAF airport may sit 30 NM away, in different terrain, and its forecast legally speaks for a 5 SM circle that does not include you. Use it as regional guidance, not as your field’s forecast.
Check the METAR’s time stamp. An hourly report can be 55 minutes old when you read it, and SPECI criteria do not catch every change that matters to a light aircraft. A ceiling sagging from 3,000 to 2,600 ft may never trigger a special report. The observation time is in the report for a reason; read it.
A TAF ages badly. A 1200Z TAF read at 2200Z was written ten hours ago from even older model data, and forecaster confidence naturally thins toward the far end of the valid period. Before a long leg, get the freshest issuance and note how old it is. Trusting hour 22 of a TAF the way you trust hour 2 is how a forecast becomes a surprise.
Watch for TAF AMD. An amended TAF replaces the previous one entirely and is issued whenever the forecaster decides the current TAF no longer represents what is happening or expected. An amendment is information in itself: something changed enough that a professional tore up the old forecast mid-shift. When you see AMD, compare it against the routine issuance and figure out what moved.
Two products, one habit. Read the TAF to build the plan, read the METAR to test it, and give your full attention to the moments when they disagree, because that disagreement is the earliest warning a text-based brief will ever give you.
Common questions
- Does every airport have a TAF?
- No. The National Weather Service writes TAFs for 715 US airports as of its June 2025 site list, while thousands more report METARs. If your field has an AWOS but no TAF, the nearest forecast airport may sit 30 NM away in different terrain, and its forecast legally speaks for a 5 SM circle that does not include you. Use it as regional guidance.
- How old can a METAR be when I read it?
- Up to about 55 minutes. Routine reports are hourly, most observed in the few minutes before the top of the hour, and SPECI criteria do not catch every change that matters to a light aircraft. A ceiling sagging from 3,000 to 2,600 ft may never trigger a special report, so read the observation time rather than assuming it is current.
- What does TAF AMD mean?
- The forecast has been amended. An amended TAF replaces the previous one entirely and is issued whenever the forecaster decides the current TAF no longer represents what is happening or expected. The amendment is information in itself: something changed enough that a professional tore up the old forecast mid-shift. Compare it against the routine issuance to see what moved.