How to Read
a TAF
Decode a Terminal Aerodrome Forecast line by line — issue time, valid period, wind, visibility, and sky — then follow the FM, BECMG, TEMPO, and PROB groups through the day.
What Is a TAF?
A TAF — Terminal Aerodrome Forecast — is the forecast counterpart to the METAR. Where a METAR tells you the weather right now, a TAF tells you what to expect for roughly the next 24 to 30 hours within about 5 statute miles of the airport. It uses the same shorthand as a METAR, with one extra idea: change groups that step the forecast forward in time.
KXXX 121730Z 1218/1318 27012KT 6SM BKN030 FM130200 24008KT P6SM SCT050 TEMPO 1306/1310 3SM BR BKN015 FM131500 30015G25KT P6SM SKC
The Header, Field by Field
Every TAF opens with the same six pieces of information before the forecast itself begins.
KXXX
Station
The ICAO identifier of the airport the forecast is for.
121730Z
Issued
Issued on the 12th at 1730 UTC (“Z” = Zulu, never local). Routine TAFs come out four times a day, near 0000, 0600, 1200, and 1800Z.
1218/1318
Valid period
Valid from the 12th at 1800Z to the 13th at 1800Z. The format is DDHH/DDHH — day and hour of the start, then the end. Most TAFs run 24 hours; busy airports run 30.
27012KT
Wind
From 270° at 12 knots — same coding as a METAR. G adds a gust, VRB is variable, 00000KT is calm.
6SM
Visibility
6 statute miles. P6SM means greater than 6 SM; M1/4SM means less than a quarter mile.
BKN030
Sky
Broken at 3,000 ft AGL. Same cloud codes as a METAR (FEW / SCT / BKN / OVC), heights in hundreds of feet.
Change Groups: How the Forecast Moves Through the Day
After the opening line, a TAF uses four kinds of group to say when and how the weather changes. This is the part that trips pilots up — get these and the rest is just METAR coding.
FM
FROM — a rapid, lasting change
FMDDHHMM. At the stated time everything that follows replaces the entire forecast until the next FM. “FM130200” = at 0200Z on the 13th, a new line takes over.
BECMG
BECOMING — a gradual change
BECMG DDHH/DDHH. Conditions transition over the stated window and then persist. Used when the change takes time, like fog lifting or a front passing.
TEMPO
TEMPORARY — brief fluctuations
TEMPO DDHH/DDHH. Short-lived swings within the window — each under an hour, less than half the period in total. The base forecast still applies between them.
PROB30 / PROB40
PROBABILITY — 30% or 40% chance
PROBxx DDHH/DDHH. A 30% or 40% probability of the conditions that follow (usually thunderstorms or low visibility). There is no PROB50 — at that confidence the forecaster states it outright.
In the example above, the airport starts marginal (broken at 3,000), clears after 0200Z, briefly drops to 3 SM in mist between 0600Z and 1000Z (the TEMPO), then turns gusty and clear from 1500Z onward.
METAR vs TAF, Side by Side
They share a vocabulary but answer different questions. You read both on every preflight: the METAR for now, the TAF for the plan.
Read the TAF in plain English
FlightKit decodes the METAR and TAF for any US airport into plain language — the valid period, every change group, and a go/no-go-ready summary — so you do not have to decode it in your head.
Keep learning
Frequently Asked Questions
What is a TAF?
A TAF (Terminal Aerodrome Forecast) is a forecast of the expected weather within about 5 statute miles of an airport, covering roughly the next 24 to 30 hours. Pilots read it alongside the METAR to plan for conditions at departure, en-route alternates, and the destination.
How often are TAFs issued and how long are they valid?
Routine TAFs are issued four times a day — near 0000, 0600, 1200, and 1800 UTC — and are typically valid for 24 hours, with busier airports getting 30-hour forecasts. When the forecast changes significantly, an amended TAF (TAF AMD) is issued off-schedule.
What is the difference between FM, BECMG, and TEMPO?
FM (FROM) marks a rapid, lasting change at a specific time that replaces everything until the next group. BECMG (BECOMING) is a gradual change over a window that then persists. TEMPO (TEMPORARY) covers brief fluctuations — each under an hour — that come and go while the base forecast still applies.
What does PROB30 mean in a TAF?
PROB30 means a 30% probability of the conditions that follow during the stated time window, usually thunderstorms or low visibility. PROB40 is a 40% chance. There is no PROB50 or higher — at that level of confidence the forecaster states the conditions directly rather than as a probability.
What is the difference between a METAR and a TAF?
A METAR is an observation of the weather happening now at an airport. A TAF is a forecast of the expected weather over the next 24 to 30 hours within about 5 SM of the airport. Read the METAR for current conditions and the TAF for what is coming.
Does a TAF cover my whole route?
No. A TAF only forecasts the area within roughly 5 statute miles of the airport it is issued for. For weather between airports you use other products — graphical forecasts (GFA), winds and temperatures aloft, AIRMETs/SIGMETs, and PIREPs.
What does P6SM mean?
P6SM means visibility greater than 6 statute miles — the “P” stands for “plus,” more than the value shown. Its opposite, “M,” means minus or less than, as in M1/4SM for visibility less than a quarter mile.