Precipitation

Precipitation is water in any form — solid or liquid — falling from the atmosphere to the earth’s surface. It includes rain, drizzle, snow, sleet, ice pellets, hail, and freezing forms of rain and drizzle. Precipitation is one of the most significant weather factors in aviation, affecting visibility, runway conditions, and airframe icing.

Precipitation Types and Their Effects

• Rain (RA): Reduces visibility; wet runways increase braking distance
• Drizzle (DZ): Fine droplets; reduces visibility; may not trigger FZRA warning if just above freezing
• Snow (SN): Visibility reduction; runway contamination; blowing snow can be severe
• Freezing rain (FZRA): Severe icing; most dangerous for airframe and ground operations
• Ice pellets (PL): Slippery surfaces; indicator of freezing rain above
• Hail (GR): Structural damage to aircraft; associated with severe thunderstorms

Precipitation in METARs

Precipitation is reported in METARs using standardized codes with qualifiers for intensity (light −, moderate no qualifier, heavy +) and type. Examples: -RA (light rain), +SN (heavy snow), FZRA (freezing rain), RASN (rain and snow mixed). Multiple precipitation types are reported together.

Related Terms

See also: Rain, Snow, Freezing Rain, Icing.