Frost

EASA defines “Frost” in one regulation. The wording below is reproduced verbatim from the EASA Easy Access Rules, with a link to the paragraph it comes from.

‘Frost’ means ice crystals formed from airborne moisture on a surface whose temperature is below freezing; frost differs from ice in that the frost crystals grow independently and therefore have a more granular texture.
Note 1: ‘Below freezing’ refers to air temperature equal to or less than the freezing point of water (0 degree Celsius).
Note 2: Under certain conditions, frost can cause the surface to become very slippery and it is then reported appropriately as downgraded RWYCC.

CS ADR-DSN.A.002 · Aerodromes · Regulation (EU) No 139/2014 · Easy Access Rules, 13 Mar 2026 revision · Read CS ADR-DSN.A.002

Also in the aviation glossary

Frost FAA PHAK: Ice crystal deposits formed by sublimation when temperature and dewpoint are below freezing.

Defined in the same article

Ask Metis where Frost applies to you →

Metis opens with Avioverse in October 2026 · request early access.