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The Pilots Desk
ICAOICAO Annex 3

ICAO Annex 3 — Meteorological Service

Read the official rule

Annex 3 standardises aviation weather service worldwide: the content and format of METARs, TAFs, SIGMETs, AIRMETs, volcanic-ash and tropical-cyclone advisories, and the meteorological information provided to crews and ATC. It's why a METAR reads the same in Tokyo as in Toronto. *Summary only — consult ICAO and your meteorological authority.*

This is an original plain-English explanation for training and reference, not legal advice and not for navigation. Always rely on the current official rule linked above. Last reviewed June 2, 2026.