I did the Grim a few years back. It was freezing cold and the lead runners got blood all down their legs from breaking the ice on the pools.
Of course, that was back then when these events took place regardless of the conditions and only real hairy-chested well 'ard chaps like me did them. Slather on some whale blubber, grab the woolly hat, string vest, shorts and Dunlop Green Flashes and we were good to go.
Nowadays, first sign of a snowflake and everyone goes home.
Wimps!!