"a storm of rain," 1804, from rain (n.) + storm (n.).
Entries linking to rainstorm
rain n.
Middle English rein, from Old English regn "rain, descent of water in drops through the atmosphere," from Proto-Germanic *regna- (source also of Old Saxon regan, Old Frisian rein, Middle Dutch reghen, Dutch regen, German regen, Old Norse regn, Gothic rign "rain"), with no certain cognates outside Germanic, unless it is from a presumed PIE *reg- "moist, wet," which may be the source of Latin rigare "to wet, moisten" (see irrigate).
Rain dance "dance performed by a tribal group in hope of summoning rain" is from 1867; rain date in listings for outdoor events, giving an alternative date should rain interrupt them on the intended day, is from 1948. To know enough to come in out of the rain (usually with a negative) "take ordinary measures for one's protection" is from 1590s. Rain-shower is Old English renscur. Rain-gauge "instrument for collecting and measuring the amount of rainfall at a given place" is by 1769.
storm n.
Old English storm "violent disturbance of the atmosphere, tempest; onrush, attack, tumult; disturbance," from Proto-Germanic *sturmaz "storm" (source also of Old Norse stormr, Old Saxon, Middle Low German, Middle Dutch, Dutch storm, Old High German sturm, German Sturm), from PIE *stur-mo-, from root *(s)twer- (1) "to turn, whirl." Old French estour "onset, tumult," Italian stormo "a fight" are Germanic loan-words. Figurative (non-meteorological) sense was in late Old English.
Storm-wind is from 1798. Storm-door first recorded 1872; storm-water is from 1847; storm-window is attested from 1824. Storm surge attested from 1872. Adverbial phrase _______ up a storm is from 1946.