Lightning may strike at any time. Capable of travelling almost horizontally for up to 10 kilometres from the storm cloud in which it originated, a thunderbolt may appear to come out of a clear blue sky, long before the storm rolls into view. The faster and
more violent the storm, the more likely this is.
And don't expect rubber-soled shoes to save you, either. If lightning has burned its way through thousands of metres of air, which is apparently a superb insulator, then a few millimetres of shoe will provide little protection.
But don't worry. The myth of the lightning-zapped victim reduced to a small heap of smoking ashes is just that, says the Lightning Strike Injury Page reassuringly. The literature shows only 20 to 30 per cent of those hit will die, while other evidence suggests the death rate may be as low as 3 per cent.
Mary Ann Cooper, the director of the lightning injury research programme at the University of Illinois, who has put this fascinating resource together, and her colleagues at Chicago medical school, argue that their specialty is a separate if emerging discipline in its
own right - they call it keraunomedicine.
Lightning injuries, they say, are quite different from high-voltage electrical trauma of the sort that doctors usually see, and while many of those hit by thunderbolts may show few external signs of injury and few, if any, burns, most will suffer permanent physiological and psychological sequelae.
Some of these are described from personal experience by Steve Mashburn, founder of the Lightning Strike and Electric Shock Survivors International support group, who was himself struck down while playing golf with friends.
He, at least, lived to tell the story. One of his golfing partners did not.