old-fashioned To rain extremely heavily. Primarily heard in UK. We've been preparing for this match for weeks, but I heard it's going to be raining stair-rods tomorrow. We were looking forward to sunny skies in Portugal, but it rained stair-rods the whole time we were there.
See also: rain
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.