I think we can trump that when we went to the Big5 O in 2012. E was 7 and we entered him on M12 (the youngest class then). 2 minutes after he set off on the first day there was the biggest scariest thunder and lightning storm I've ever been out in, with hailstones the size of marbles. It was terrifying and I have a clear memory of an adult out on his course sheltering under a tree, too terrified to move (not the smartest place to hide). E got lost trying to find the first (orangeish) control but somehow managed to find his way round the rest of the course. Then he stood waiting for us in the storm at the finish until S-JB and NB found him there and sent him back to the car.
Doesn't seem to have had any long term effect on him :-)
Hmm, yes that was an epic race - not helped by the colours on my map gradually wiping off in the wet... started with yellow, then green, only once blue and brown started to go did I realise what was happening.