rain off (usually passive)
Definition: to stop something happening because it is raining.
E.g.1: We had planned to have a picnic yesterday, but it was rained off. We’ll have the picnic when the weather improves.
E.g.2: A: Are you going to watch the cricket match today?
B: No. It’s been rained off. They are going to play
it next weekend, if it doesn’t rain!
This phrasal verb cannot be separated.