The Night Horseman by Max Brand

When they rode out of the town the wet sand squashed under the feet of their horses and splashed up on their riding boots and their slickers. It even spotted their faces here and there, and a light brown spray darted out to right and left of the falling hoofs. For all the streets of Elkhead were running shallow rivers, with dark, swift currents, and when they left the little town the landscape was shut out by the falling torrents. It made a strange and shifting panorama, for the rain varied in its density now and again, and as it changed hills which had been quite blotted out leaped close upon them, like living things, and then sprang back again into the mist.

So heavy was that tropical fall of water that the horses were bothered by the beating of the big drops, and shook their heads and stamped fretfully under the ceaseless bombardment. Indeed, when one stretched out his hand the drops stung him as if with lashes of tiny whips. There was no wind, no thunder, no flash of lightning, only the tremendous downpour which blended earth and sky in a drab, swift river.