Reading and understanding a TAF

A TAF is the forecast for an aerodrome. It uses the same abbreviations as a METAR but adds times and change groups. That is exactly where most reading errors are made.

Applicability: European Union (EASA framework); provided in Germany by the Deutscher Wetterdienst (the national meteorological service)
Rulemaking authority: Commission Implementing Regulation (EU) 2017/373, Annex V (Part-MET), MET.OR.220 and MET.TR.220
Reviewed by NorthTrack on: 2026-09-13

Validity

A routine TAF is valid for 9, 24 or 30 hours, unless the competent authority determines otherwise for aerodromes with fewer than 9 operating hours (MET.TR.220(c)). It is filed for transmission no earlier than 1 hour before the start of its validity period (point (d)). For any one aerodrome only one TAF may be valid at a time (MET.OR.220(b)) – a new TAF replaces the old one entirely.

The practical consequence
If you are reading two TAFs side by side, you are reading one too many. The one that counts is always the most recently issued. A correction appears as TAF AMD (amended) or TAF COR (corrected).

The order of the elements

MET.TR.220(a) lays down which elements appear, and in what order:

type of forecast (TAF)
location indicator
time of issue
identification of a missing forecast, where applicable (NIL)
date and period of validity
identification of a cancelled forecast, where applicable (CNL)
surface wind
visibility
weather
cloud
expected significant changes to those elements during the validity period

A TAF therefore forecasts exactly four weather elements – wind, visibility, weather and cloud – plus their changes. Temperature, dew point and QNH are not part of the standard content of a TAF.

The change groups

The change-group abbreviations

These abbreviations carry the real message of a TAF — they say when something happens and how certain it is.

NOSIG — No significant change
The TREND in a METAR: no significant change in the next 2 hours.
BECMG — Becoming
The state changes gradually within the window given and stays that way afterwards.
TEMPO — Temporary
A temporary departure from the base state; the base state continues to apply.
PROB — Probability
Only PROB30 or PROB40, and in a TAF always tied to a TEMPO group.
FM — From
The start of a change period, or of a new forecast section.
TL — Till
The end of a change period.
AT — At
The time of a change in a TREND.
TX — Maximum temperature
A temperature forecast in a TAF, used in only a few countries.
TN — Minimum temperature
A temperature forecast in a TAF, used in only a few countries.

FMddhhmm
Meaning: From – a new, complete set of conditions applies from this time · How to read it: Everything before it has ended. The group describes the new state in full, from scratch.
BECMG ddhh/ddhh
Meaning: Becoming – the transition takes place within the window given · How to read it: The elements named change gradually and then stay that way. Elements not named remain unchanged.
TEMPO ddhh/ddhh
Meaning: Temporarily – temporary fluctuations within the window · How to read it: Short-lived each time, not continuous. The base state continues to apply.
PROB30 / PROB40
Meaning: A probability of 30% or 40% respectively · How to read it: Used alone or together with TEMPO. Higher probabilities are not expressed as PROB but forecast outright.

TEMPO is not a footnote
A TEMPO group describes conditions that must be reckoned with inside the window. For alternate and fuel planning it is normally the less favourable of the two states that is relevant, not the base state.

Rules for the individual elements

Wind: what is forecast is the expected prevailing direction. Where it cannot be forecast, VRB is used. Gusts are given when the peak exceeds the mean speed by 10 kt or more.
Visibility: below 800 m in steps of 50 m, from 800 m to below 5 km in steps of 100 m, from 5 km to below 10 km in steps of 1 km, and from 10 km as 9999 – unless CAVOK is forecast.
Weather: at most three phenomena, each with its intensity.
Cloud: as in a METAR; CB and TCU are named explicitly.

Example – a 30-hour TAF with every change group

A TAF with TEMPO, BECMG and PROB

TAF EDDL 131100Z 1312/1418 25010KT 9999 BKN025 TEMPO 1312/1316 24015G28KT 4000 SHRA BKN012CB BECMG 1320/1322 21006KT PROB30 1402/1408 1500 BR BKN004

TAF EDDL — Aerodrome forecast for Düsseldorf.
131100Z — Issued on the 13th at 11:00 UTC – exactly 1 hour before validity begins, so at the earliest time permitted.
1312/1418 — Valid from the 13th at 12:00 UTC to the 14th at 18:00 UTC. That is 30 hours – one of the three permitted periods.
25010KT 9999 BKN025 — Base state: wind from 250° at 10 kt, visibility 10 km or more, broken at 2,500 ft.
TEMPO 1312/1316 24015G28KT 4000 SHRA BKN012CB — Between 12:00 and 16:00 UTC on the 13th, at times: wind 15 kt gusting 28 kt, visibility 4,000 m, rain showers, broken cumulonimbus at 1,200 ft. For planning inside that window, this is the state that governs.
BECMG 1320/1322 21006KT — Between 20:00 and 22:00 UTC on the 13th the wind gradually backs to 210° and eases to 6 kt – and stays that way afterwards. Visibility and cloud are not named and therefore continue unchanged.
PROB30 1402/1408 1500 BR BKN004 — With a 30% probability between 02:00 and 08:00 UTC on the 14th: visibility 1,500 m, mist, broken at 400 ft. The classic overnight cooling once the wind has dropped away.

A constructed teaching example. The location indicators are real ICAO indicators; the weather itself is invented. For an actual flight, only the current report from an official source applies.

Common pitfalls

BECMG changes only the elements it names. Whatever is not named continues unchanged. This is often misread as "everything will be fine".
There is no TEMPO without named elements – and here too, elements not named stay as they were.
The validity period is not the issue period. 131100Z 1312/1418 means: issued at 11:00, valid from 12:00.
A TAF applies to the aerodrome, not to the route. What happens en route is in SIGMET, area forecasts and charts.

Practise reading TAF and METAR in the weather modules of the NorthTrack app. Open the NorthTrack app

Official sources

European Commission / EASA: Commission Implementing Regulation (EU) 2017/373 (Annex V "Part-MET", Annex VI "Part-AIS") – Consolidated version 02017R0373-20250501. Open source (retrieved 2026-09-13)
Deutscher Wetterdienst (DWD), the German national meteorological service: METAR / TREND / TAF – aviation weather reports and forecasts (bilingual code tables) – DWD 134, edition 01/2024. Open source (retrieved 2026-09-13)
Deutscher Wetterdienst (DWD), the German national meteorological service: The DWD aviation weather service – advice and self-briefing (German site) – continuously updated. Open source (retrieved 2026-09-13)