Numerous nearby lightning strikes!
Hail, more hail, and still more hail! (usually it lets up after a minute or two.)
Rain so fast and furious that the gutters couldn't keep up and water spilled along the entire length.
The glen out front was standing water and a stream ran through the backyard towards the driveway access.
The hail created diagonal patterns or ricocheting white off of the roof angles.
And even now, with the sun out, the rain over, everything is dripping furiously and the lightning still strikes nearby!
That was a storm!