lash down on (someone or something)
Of rain, to fall very heavily on someone or something. I love the sound of rain lashing down on the roof of the house at night. It's dry at the moment, but those dark clouds look like they could lash down on us at any moment.
lash down on someone or something
[for rain] to beat down on someone or something. The wind and rain lashed down on us. The rain lashed down on the young plants and pounded them into the soil.