Years ago I was driving home from work when I ran into a hail storm with golf-ball sized hail. I wanted to shelter under a bridge but others got there first, so I carried on slowly watching the mirror for speed-crazed truck drivers. I expected dents and maybe a cracked windsheild but nothing of the sort, but when I got home I discovered I had narrowly missed a tornado. It had destroyed a shopping mall and tossed trucks around like toys, leaving a swathe of damage over a hundrd clicks long. I still recall the color of the sky: green.