In the summer of 1984 the inhabitants of Munich discovered just how dangerous hail can be. After a relatively cool start to the season, the city became very hot within just a few days. The temperature climbed to 37C, but only a few days later a cold front moved across Germany, with catastrophic consequences. Hailstones the size of tennis balls beat down on Munich, causing damage worth over 1.5 billion Euros.
Hailstones 25m/s (90km/h) up to 100mm
Rain drops 8m/s (29km/h) 0.6-3mm
Snowflakes 0.8m/s (2.88km/h) 5-30mm
Huge hailstones like these occur when hot, humid air collides with cooler layers of cloud, causing unusually strong updraughts.