How do I decode a TAF?

Read it left to right: TAF (with AMD if amended), the ICAO station code, the issue time (DDHHMMZ), the validity period (DDHH/DDHH), then wind, visibility, weather and cloud for the base forecast, followed by change groups such as FM, BECMG, TEMPO and PROB30/40. Paste the full string above to have each part translated.

How do I read the TAF issue time and validity, such as 051151Z 0512/0612?

051151Z means the TAF was issued on day 5 of the month at 11:51 UTC (Z = Zulu, or UTC). 0512/0612 means it is valid from day 5 at 12:00 UTC to day 6 at 12:00 UTC, a 24-hour period. An end hour of 24 means midnight at the end of that day.

A Terminal Aerodrome Forecast (TAF) is the standard ICAO format for aerodrome weather forecasts. In the US it covers the area within 5 statute miles of the runway complex and is issued four times a day (00, 06, 12 and 18 UTC) for 24 or 30 hours, with amendments as needed. It uses the same weather codes as a METAR, arranged in time-based change groups.

What is the difference between BECMG and TEMPO?

BECMG (becoming) is a lasting change that happens gradually during the window, normally within 2 hours and never more than 4 under ICAO; after the window the new conditions prevail. TEMPO is a temporary fluctuation: each episode lasts less than an hour and together they cover less than half of the window, after which the prevailing forecast resumes.

What does FM mean in a TAF?

FM (from) marks a rapid, complete change starting at the given time, written FMDDHHmm. FM051430 means from day 5 at 14:30 UTC. Everything after FM replaces the previous forecast, so an FM group always repeats wind, visibility and sky condition.

What is PROB30 or PROB40?

PROB30 or PROB40 gives a 30% or 40% chance of the described conditions during the following window; PROB40 TEMPO means a 40% chance of temporary fluctuations. These are the only valid probability values. US National Weather Service TAFs use PROB30 only and not in the first 9 hours.

What does VCFG or VCSH mean in a TAF?

VC means in the vicinity: forecast near the airport but not at it. ICAO defines vicinity as about 8 km from the aerodrome perimeter; US TAFs use 5 to 10 statute miles from the airport center. VCFG is fog in the vicinity and VCSH showers in the vicinity; the decoder shows them as "In the Vicinity — Fog" and "In the Vicinity — Showers".

What do TX and TN mean at the end of a TAF?

They forecast the maximum and minimum temperature and when they occur. TX25/0414Z means a high of 25 °C on day 4 at 14:00 UTC, and TNM02/0506Z means a low of minus 2 °C on day 5 at 06:00 UTC (M = minus). They are common outside the US and in military TAFs.

What does WS020/27045KT mean in a TAF?

It forecasts non-convective low-level wind shear: at 2,000 ft above ground the wind is from 270° at 45 knots, very different from the surface wind. US TAFs add it when shear is expected within 2,000 ft AGL.

How do I read cloud layers like BKN025CB?

The sky condition group has coverage (FEW = 1–2 oktas, SCT = 3–4, BKN = 5–7, OVC = 8), height in hundreds of feet AGL, and an optional suffix CB (cumulonimbus — thunderstorm) or TCU (towering cumulus). BKN025CB means broken cumulonimbus at 2,500 ft AGL. The lowest BKN, OVC or VV layer is the ceiling.

What does NSW mean in a TAF?

NSW (No Significant Weather) cancels previously forecast weather in a BECMG or TEMPO group, showing that the rain, snow or other phenomenon is expected to end.

TAF Decoder

Paste a raw ICAO or US TAF and get a plain-English breakdown of validity, wind, visibility, weather, cloud layers, temperature, icing and turbulence groups, every change group, and an hour-by-hour flight-category timeline.

A TAF decoder turns a raw Terminal Aerodrome Forecast into plain English: station, issue time, validity period, wind, visibility, weather, cloud layers and each BECMG, TEMPO, FM or PROB change group.

Paste TAF String

Paste the full raw TAF string including station ID and validity period. Multi-line or single-line input is accepted.

Try a sample:

TAF Decoding Key

Common TAF groups in ICAO Annex 3 / WMO FM 51 format and the US variations in FAA Advisory Circular 00-45.

Group	Example	Meaning
Header	TAF AMD KJFK 041720Z 0418/0524	Amended TAF for JFK, issued day 4 at 17:20 UTC, valid day 4 18:00 to day 5 24:00 UTC (COR = corrected, NIL = no TAF, CNL = cancelled)
Change	FM050200	From day 5 at 02:00 UTC everything is replaced by the conditions that follow
Change	BECMG 0420/0422	Gradual lasting change between 20:00 and 22:00 UTC on day 4
Change	TEMPO 0422/0424	Temporary fluctuations, each under 1 hour and in total under half the window
Change	PROB30 0506/0512	30% probability during the window (PROB40 = 40%; PROB40 TEMPO combines both)
Wind	27015G25KT	From 270° at 15 kt gusting 25 kt (direction true; MPS or KMH units outside the US)
Wind	VRB05KT · 00000KT	Variable direction at 5 kt · calm
Wind	WS020/27045KT	Low-level wind shear: wind at 2,000 ft AGL from 270° at 45 kt
Visibility	P6SM · 3SM · 1 1/2SM	More than 6, 3 and 1½ statute miles (US)
Visibility	9999 · 4000 · CAVOK	10 km or more · 4,000 m · ceiling and visibility OK (≥ 10 km, no cloud below 5,000 ft or CB, no weather)
Weather	-SHRA · +TSRA · VCSH	Light rain showers · heavy thunderstorm with rain · showers in the vicinity
Weather	BR · FG · FZFG · HZ	Mist (vis ≥ 1 km) · fog (< 1 km) · freezing fog · haze
Weather	NSW	No significant weather (ends forecast precipitation)
Cloud	FEW · SCT · BKN · OVC 030	1–2, 3–4, 5–7, 8 oktas at 3,000 ft AGL; BKN and OVC form a ceiling
Cloud	BKN020CB · VV002 · SKC · NSC	Cumulonimbus layer · sky obscured, vertical visibility 200 ft · sky clear · no significant cloud
Temperature	TX25/0414Z TNM02/0506Z	Max 25 °C on day 4 at 14 UTC; min −2 °C on day 5 at 06 UTC
Icing	620304	6 · type 2 (light in cloud) · base 030 = 3,000 ft · thickness 4,000 ft
Turbulence	530005	5 · type 3 (moderate in clear air, frequent) · base 000 = surface · thickness 5,000 ft
Other	QNH2992INS · AMD NOT SKED	Lowest altimeter 29.92 inHg (military) · amendments not scheduled (remark)

FAA Flight Categories

The worse of ceiling (lowest BKN, OVC or VV layer) and visibility sets the category.

Category	Ceiling	Visibility
LIFR Low IFR	below 500 ft	below 1 SM
IFR IFR	500 to below 1,000 ft	1 to below 3 SM
MVFR Marginal VFR	1,000 to 3,000 ft	3 to 5 SM
VFR VFR	above 3,000 ft	above 5 SM

Quick answer

A TAF decoder turns a raw Terminal Aerodrome Forecast into plain English: station, issue time, validity period, wind, visibility, weather, cloud layers and each BECMG, TEMPO, FM or PROB change group. Most TAFs cover a 24- or 30-hour window for one airport.

Examples

TAF KJFK token	Meaning
041720Z	Issued day 4 at 17:20 UTC
0418/0524	Valid day 4 18:00 to day 5 24:00 UTC
27015KT	Wind from 270° (W) at 15 knots
P6SM	Visibility more than 6 statute miles
BKN040	Broken clouds at 4,000 ft

Paste any TAF or tap a sample to decode every group in plain English and see an hourly VFR/IFR timeline.

Summary

The TAF Decoder parses any ICAO or US Terminal Aerodrome Forecast into clearly labeled sections. It handles the base forecast and all change groups — FM (from), BECMG (becoming), TEMPO (temporary), PROB30/PROB40 and INTER — and decodes wind (including 3-digit speeds and gusts), visibility in statute miles or metres, weather, cloud, wind shear, TX/TN temperature, icing and turbulence groups. An hourly timeline shows the prevailing FAA flight category and any temporary or probable worsening across the validity period. Tokens it cannot translate are listed rather than hidden. All processing runs in your browser.

How it works

Paste or type a raw TAF string into the input field — include everything from the ICAO station ID onward.
Click "Decode TAF" or press Enter to parse the forecast.
The base forecast section appears first, showing validity period, wind, visibility, weather and cloud layers, with an AMD or COR badge for amended or corrected forecasts.
Each change group (FM, BECMG, TEMPO, PROB) appears as a separate card with its own time window and the flight category that results when its changes are applied to the prevailing forecast.
The hourly timeline shows the prevailing category (base, FM and completed BECMG changes) and, on a second row, the worst category from TEMPO, PROB or in-progress BECMG groups.
Use the sample buttons to explore real-world TAF formats before entering your own.

Use cases

Quickly understand a TAF during preflight planning without memorizing ICAO codes.
Spot IFR and LIFR periods on the hourly timeline when choosing an alternate airport.
Teach student pilots how Terminal Aerodrome Forecasts are structured.
Decode military and Canadian TAF icing (6xxxxx), turbulence (5xxxxx) and QNH groups.
Cross-check decoded values against ForeFlight or official aviation weather services.
Study for the FAA private or instrument written exam.

Frequently Asked Questions

Last updated: 2026-10-09 · Reviewed by Nham Vu