bucket down BrE informal
rain buckets
come down in buckets

"Raining buckets, it is," the steward said.

Outside, it abruptly rained buckets.

Lately trouble had been raining buckets.

"Back home, I'd have storms up and raining buckets!"

In one room it was raining buckets.

He said it was raining buckets and nobody saw them.

As the night slowly fell, a storm blew up and it rained buckets.

It was mid-October, and already, through much of September, it had rained buckets.

By now it was raining buckets.

Every time I got down to the farm, it rained buckets, and the ground was like cement.