there was a strong thunderstorm last Friday in “my” Düsseldorf area, with a of rain, see http://www.rp-online.de/public/article/duesseldorf-stadt/728102/Unwetter-legt-Duesseldorf-lahm.html. The temperature went down from 30 to 20°C within half an hour. Fortunately, we are living on a small hill with very low probability to get damaged by the water.

Cheers
Ralf