You hit the nail on the head with the cooler than average temperure concept. In fact, I personally cannot recall a summer with so many relatively cool maximum temperatures as this summer for such an extended period of time! Yes I know we had a few episodes of heat but it is infrequent. Usually by January the heat really begins to set in for longer periods. Tomorrow seems like another cooler day with localised instability - perhaps storms moving in from the coast inland.
Took a look at some of the latest footage including the 9th December 2007 hailstorm and also the most recent hailstorms I intercepted - some half decent footage. This year is one of those years where top footage is hard to come by.