I wouldn't worry about it too much, I think of plenty of fantastic summers
which started a bit on the dodgy side.

The summer of 1990 springs to mind as a very good example where the jet
stream was far south and low pressure after low pressure dominated the
weather until the first week of July then it was like a switch and suddenly
out came the sun and the warmth. The rest of the summer was a scorcher.

I believe the summer of 1976 didn't really get going until mid-June?

And the best summer I have ever known (was a bit young to remember 1976
properly) was quite unsettled until the 3rd week of June, that was 1995,
which I regard as the last really settled summer we've had.
________________
Nick.
Otter Valley, Devon
83 m amsl
http://www.ottervalley.co.uk