Have gone in June twice. It is a great time to go if you do your homework. Hot-sure. Afternoon thunderstorms-sometimes. Crowds-definitely, its summer vacation! Do your research, GET THERE EARLY, use the fastpass system, take breaks,and you will have an awesome time. The parks are open late and there are lots of parades and fireworks scheduled.
My added advice would be
-Get there EARLY. I am saying this again because it is unreal how much more you can accomplish when you push your family to do this.
-Don't fuss with makeup or hair. Pull your hair in a pony, slap on some sunscreen, sunglasses and a smile and you will be good to go.
-Bring more clothes. I thought we would need less clothes since it was summer but I was wrong. If we went back to our condo, everyone wanted to get out of their sweaty clothes. So we needed extra t- shirts, shorts, socks undies. I always do laundry on vacaction but if you don't want to, bring some extra changes.
-Sundresses look and feel great and are nice for dinner and the parks.
-Bring a pair of extra sneakers. We got caught in a downpour and not everyone in my family had an extra pair of good walking shoes. Our sneakers took some time to dry out.
-If you are pushing a stroller, bring a raincover for it as drying out a stroller after a downpour can also be a problem
- Stay hydrated. You can get cups of ice from the stands for free. Once you are thirsty, you are already dehydrated.
-Read all the heat related info you can. Bring your fans and you will have a wonderful Time!