OK, I'll make an educated guess about this. Last couple of years we've been suffering the effects of La Nina. (low pressure in the eastern pacific) one of the results of this is that it pulls the Jetstream south, and one of the effects of that is that the Icelandic low pressure region fills, and the Azores high pressure region (what makes our summers) moves further south. and the upshot of all that is mild and wet weather. Now, the La Nina weather effect has decreased, hence the colder winter we've had, so if everything being normal, we should see a return to more usual summer weather patterns.