Summer at WDW is very hot and it rains every day.
But....
If you change you strategy, it is very enjoyable. In a lot of ways, I prefer summer.
In general, the parks are open much later in the summer than in other seasons. And everything is open...nothing is closed for refirb. If you plan to go to the parks at opening, take a break from 1 pm to 5 pm, then stay until closing,
you will still have an opportunity to stay in the parks for a very long time, you will avoid the wonnnnrst part of the crowds,
you will avoid the worst part of the heat,
you will get to enjoy the beauty of WDW at night, and
you will save money by eating lunch or an early supper off-site.