A hydrometeor is the WMO's generic term for any aqueous particle in the atmosphere. They are classified as precipitating (rain, snow, hail, drizzle, graupel) and non-precipitating (fog, mist, dew, hoarfrost, rime).
Radar classification
Modern dual-polarisation weather radars can distinguish hydrometeor types (rain, wet snow, hail, etc.) by analysing particle shape and orientation. This automatic classification is essential for aviation icing warnings and hail alerts.