The rain was heavy, grew heavier, then the thunder started in and, within a few moments, the hail began to fall, rather big hailstones, very big ones, dense, breaking, pounding on the skylights. The top photograph shows the street outside running like a shallow river with an ice floe shattered into a mobile mosaic drifting down the middle.
The whole thing lasted about half an hour then started to clear and within an hour it was sunny again. But cold. It is August after all. I am sure there must be some ancient weather saw for this, such as:
When in August falls the hail
Closely following on rain
To beat in fury on the pane..
Prepare to bring out spade and pail
Let Dick the Shepherd blow his nail.
Let all the weather forecasts fail.
Let traffic crawl as slow as snail.
Let stores prepare a Christmas Sale...
etc etc ad inf