In the UK it's "Ne'er cast a clout (vest or undershirt) till May be out" meaning the may flowers or hawthorn. For the first time in a long while, the may was not out this weekend, but the rhododendrons were. I can't remember what that means weather-wise, but I'm keeping me big knickers to hand!

Flanders and Swann put it more succinctly... from the 'Song of the Weather' - "Farmers fear unkindly May, frost by night and hail by day!"

LTS