Spoil one's plans, as in The minority party in the legislature has tried hard to rain on the speaker's parade, but so far his agenda has prevailed. This expression conjures up the image of a downpour ruining a celebration such as a parade. [c. 1900]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.