Definition
A form of frozen precipitation made up of tiny, slowly falling ice particles, reported in a METAR using the code IC. Ice crystals form directly from water vapor in very cold air, typically at temperatures well below freezing, and often appear as a fine sparkle or haze in the air rather than as visible flakes.
Plain English
Very small bits of ice falling slowly through the air, reported on a weather report with the letters IC. They form in extremely cold air and look more like a shimmering fog than snow.
Context Anchor
Seen in the weather section of a METAR when very small ice particles are present in the air.
Derivation
Ice comes from Old English, meaning frozen water. Crystal comes from a Greek word meaning ice or clear ice-like stone. Together, ice crystals means small, solid pieces of frozen water with a crystal-like form.
Why Pilots Care
Signals possible high-altitude icing or visibility restrictions that may affect route, altitude, or aircraft performance decisions.
Grounding Statement
Picture tiny sparkling ice particles hanging in very cold air and making distant objects harder to see.
Intuition Check
Do not read IC as aircraft icing. In a METAR, IC reports ice particles in the air at the observation point.
Example Sentence 1
The METAR for the northern airport reported IC, indicating ice crystals were falling in the still, frigid morning air.
Example Sentence 2
The forecast mentioned IC, so the pilot planned a higher cruise altitude to avoid any icing risk.