TO RAIN/PISS ON SOMEONE’S PARADE [circa 1900 for ‘rain,’ 1970s for ‘piss’ and both still in use] (U.S. origin): This chiefly North American colloquialism means to spoil someone’s plans or celebration, prevent someone from enjoying an occasion or event, to shatter illusions, or to ruin an otherwise satisfactory situation. “The minority party in the legislature has tried hard to rain on the speakers parade, but so far his agenda has prevailed.” The expression, which is often heard as ‘rain on your parade,’ calls up images of a downpour spoiling elaborate floats and dampening spirits.
(Cassell’s Dictionary of Slang, Facts on File Dictionary of Clichés, American Heritage Dictionary of Idioms, Brewer’s Dictionary of Phrase and Fable)<1990 “But the opposition Labor Party, which has long sought to rain on the Lords’ parade, is once again aiming at those men and women.”—in New York Times by Sheila Rule on a plan to replace Britain’s House of Lords with an elected second chamber.>
<1999 “Would we Conservative wets please now shut up and stop raining on William Hague’s parade?” —The Times, 23 October>
Ken G – July 8, 2004