Rime is a white or milky opaque granular deposit of ice. It occurs when supercooled water droplets strike an object at temperatures at or below freezing. Factors favoring the formation of rime are small drop size, slow accretion, a high degree of supercooling, and rapid dissipation of latent heat of fusion. Rime is a result of freezing drizzle and looks like frost in a freezer. Rime icing which forms on aircraft can seriously distort airfoil shape, therefore diminishing lift and performance. Rime icing is more likely to form in stratus-type clouds with temperatures between 0C and minus 22C. When formed in cumuliform-type clouds, temperatures range from minus 9C to minus 15C and are accompanied by clear icing which is then termed mixed icing.

Glaze is a coating of ice, generally clear and smooth. It occurs when supercooled water droplets deposited by rain, drizzle, fog, or condensed water vapor strike an exposed object at temperatures at or below freezing. Factors favoring formation of glaze are large drop size, rapid accretion, slight supercooling, and slow dissipation of the latent heat of fusion. Glaze is denser, harder, and more transparent than rime and looks similar to an ice cube. Clear icing forms on aircraft and adds appreciably to the weight of the craft. This additional weight has an even greater effect in reducing the performance of the aircraft than does rime icing. Clear icing occurs in cumuliform-type clouds at temperatures between 0C and a minus 9C. It also occurs with rime icing in cumuliform clouds at temperatures between minus 9C and minus 15C.

Drifting and blowing snow are the result of snow particles being raised from the ground by the wind. To classify wind-driven snow as drifting snow, the particles will only be lifted to shallow heights (less than 6 feet) and the horizontal visibility will remain at 7 miles or more at eye level (6 feet). When the wind drives snow to levels 6 feet or higher and the visibility is restricted to 6 miles or less, it is classified as blowing snow.

Spray and blowing spray occur when the wind is of such force that it lifts water droplets from the water surface (normally the wave crests) and carries them into the air. To be classified as spray, the wind-driven water droplets will not obstruct visibility at eye level (6 feet on shore and generally 33 feet at sea). Blowing spray occurs when the water droplets are lifted in such quantities that they reduce visibility to 6 miles or less at eye level.

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