I think it is more to do with the sustained high temperatures coupled
with a diminishing water table - even here in the South West. It's
true we've had a few heavy storms, but there has been very little in
the way of persistent rainy periods. Several of the months this year
have been the driest on record and a few thunderstorms are not going to
counteract that. High temperatures and sunshine mean that large plants
and trees are pumping huge quntities of water. When that is freely
available, the result is lush green growth. When available ground
water dimishes, plants respond by getting rid of excess foliage. I've
seem this kind of 'premature-autumnation' (!!!*!!!) many times before
and it has never preceded an early true autumn or winter.

A couple of years ago this happened followed by September rains, which
brought spring growth on some trees! First frosts didn't arrive until
the following mid January and then they were only slight. We are in
for cooler, fresher nights over the next few days due to the wind being
in the east. It has to travel across a relatively cold North Sea and
coupled with clear nights, temperatures are bound to be dip after
sunset. In the far north it could mean a few very light ground frosts,
but way of compensation most of us are in for hot sunny weather that is
far more bearable due to lower humidity and cool nights.

I've been using a US method of measuring 'growing heat units' or
'growing degree days as they say over there. Basically it looks at the
average amount of heat above a base-line on any one day and is
accumulated over the year. It gives an interesting insight into how
warm a period is from a growing point of view. Not much point if you
only have hardy plants, but useful for those of us growing exotics.
Using a base of 15.6C. (60F) June this year was about 12% warmer than
June 2005 and in just 2 weeks of July, we've had over 30% more heat
than the whole of this June and 75% of last July's total. This is a
warm summer. Ooops, getting a bit anorak-ish :|