We went May/June in 2010 for the first time too after three trips in February. For us we preferred the May weather. Its is hotter and more humid, you can get huge downpours late afternoon,but its nice to walk around in shorts and t shirts, most of the time the rain stops as quickly as it starts, only once at the end of our holiday did it rain all evening.
You just need to plan your holiday differently, parks am, pool/shopping or snooze afternoon then back to the parks in the evening.Some evenings we would swim and relax around the pool.
DH and i thought there was a better buzz around the parks that time of year(don't know why but thats how it felt), and also it might be the only hot sunny weather we get knowing our unreliable British weather.