METAR weather code reference for IC (Ice Crystals)
Also known as diamond dust, ice crystals are tiny, unbranched ice particles that fall from a clear or nearly clear sky. They are most common at very cold temperatures (below -30C) and can create optical phenomena like sun dogs and halos. Often observed at high-altitude airports in arctic regions.
Here are common ways IC appears in real METAR observations:
IC-ICIC FGThese METAR codes are commonly seen alongside IC or describe related weather phenomena:
Frozen precipitation in the form of ice crystals, most often occurring as snowflakes. Snow significantly reduces visibility and is a primary concern for aircraft icing, runway contamination, and braking action. Often reported with intensity modifiers.
Very small, white, opaque grains of ice that are essentially the frozen equivalent of drizzle. Snow grains are flat or elongated, usually less than 1 mm in diameter, and fall in small quantities from stratus clouds. They rarely reduce visibility significantly.
Indicates that liquid precipitation is freezing upon contact with surfaces at or below 0 degrees Celsius. Freezing rain (FZRA) and freezing drizzle (FZDZ) are among the most dangerous weather conditions for aircraft, causing rapid ice accumulation on wings, control surfaces, and engine inlets. Freezing fog (FZFG) deposits rime ice on exposed surfaces.