Plain English Meaning
The 'extra notes' section at the end of an aviation weather report. Anything important that doesn't fit in the standard format gets added here.
Full Definition
A coded section at the end of a METAR or SPECI weather report that contains additional information not covered by the main body of the report, such as significant weather observations, automated station type, sea-level pressure, hourly precipitation, and other supplementary details.
Context Anchor
Seen in METAR weather reports, usually near the end of the report after the main weather information.
Derivation
RMK is a shortened form of “remarks.” Weather reports use many shortened forms so important information can be transmitted in a compact, standard way.