You can blame it on global warming or not as you choose but the fact is Summer temperaatures in most of the world have been slowly rising for quite a few years. It doesn't seem as though a few degrees difference in the averages from one year to the next amount to much but they really do.
My theory on, so called, global warming.....a natural earth-cycle occurence accelerated, possibly, from deforestation. I never have been "sold" on the 'hole in the ozone' mumbo-jumbo.