International METAR and TAF Format: What Changes Abroad

The international METAR format is the same product you already read, with different units and a few groups that never appear in the United States.

Nothing about the structure changes. The order of the groups is identical, and the cloud and weather codes are the same. What changes is how numbers are written and what gets appended at the end.

Units are the main difference

Two units account for most of the confusion, and both are worth checking deliberately rather than reading by habit.

Visibility abroad is in metres, given as four digits. 9999 means ten kilometres or more, and it is the top of the scale. Below that the digits are read literally, so 0800 is 800 metres and 4000 is four kilometres.

A US report gives statute miles instead, as 10SM or 1 1/2SM.

Pressure abroad is hectopascals in a Q-group. Q1013 is 1013 hectopascals. A US report gives inches of mercury in an A-group, so A2992 is 29.92 inches.

Those two are the same pressure. Reading one as the other is the classic international error, and the full comparison works through the conversion and the altitude error it causes.

CAVOK

CAVOK is the group with no US equivalent at all, and it does more than it appears to.

It replaces the visibility group, the weather group and every cloud group at once. One word instead of three sections.

Three things must be true at once. Visibility of ten kilometres or more. No cloud below 5000 feet, or below the minimum sector altitude if that is higher, and no storm cloud at any height. And no weather worth reporting.

What it does not mean is clear sky. A field can report CAVOK with a solid overcast at 8000 feet, and strong gusting wind, since wind lives in its own group.

Trend groups replace US remarks

US METARs carry a long remarks section. Most other countries do not, and use a trend group instead.

A trend is a short forecast for the next two hours, appended to the observation. NOSIG means no significant change is expected, and it is the most common.

Where a change is expected, the trend uses the same words a TAF does. BECMG for a gradual change, TEMPO for brief fluctuations, each with a time.

So an international METAR often ends with a small forecast. A US one ends with a pile of measurements instead. Sea-level pressure, the tenth-of-a-degree temperature, hourly rainfall and the peak wind are all US habits.

Temperature and other small differences

A few smaller things catch people who only fly in one place.

Negative temperatures use an M prefix in both systems, so M02/M05 is two below zero with a dew point of five below.

Runway state groups appear in many countries and rarely in the US. They give contamination, how thick it is, and braking action as a compact digit string appended after the pressure.

Some regions report QFE as well as QNH. QFE is the pressure at the field surface, so an altimeter set to it reads zero on the ground rather than field elevation. That is a different setting, not a different unit.

TAFs abroad

The international TAF differs less than the METAR does, because a forecast carries no remarks to lose.

The change groups are identical: FM, TEMPO, BECMG, PROB30 and PROB40. Valid periods use the same four-digit day and hour form.

Visibility switches to metres in the same way, and CAVOK appears in forecasts as often as in observations.

The one real difference is what surrounds it. Many countries issue no AIRMETs at all, so the moderate-level hazard advisories you may be used to simply do not exist, and the aerodrome forecast carries more of the load.

Station identifiers give it away

You can often tell which conventions a report follows before you read it.

The first letter of the ICAO identifier marks the region. K is the contiguous United States. C is Canada. E covers northern Europe, L southern Europe, Y Australia, R much of east Asia.

A K field will use statute miles and inches. Most of the rest use metres and hectopascals. Canada is the odd one, using statute miles like the US.

It is a rule of thumb, not a law. Read the group rather than trusting the prefix. But it is a useful prompt to slow down when the first letter is not the one you are used to.

Verdict on the international METAR format

Read the letter before the number and most of the difference disappears. Q is hectopascals, A is inches, four bare digits are metres, and SM is statute miles.

Then watch for the two groups with no US equivalent. CAVOK, which hides three groups behind one word and still allows an overcast at 8000 feet, and the trend group, which turns the end of an observation into a short forecast.

Last updated August 29, 2026