We have been the last three Mays and are going again this May. Temps are moderate mid 80s, but we did have some days that were heavy downpours most of the day. Don't underestimate the possibility of rain. It doesn't have to ruin your trip, but you might want to be prepared with ponchos, extra pair of shoes (since yours will need to dry more than overnight to be wearable), stroller cover if you are using a stroller. If you are planning a water park, it gets a little tougher because you can't really just tour through the rain at a water park like you can in a park. So you might need to switch days around at the last minute, which can wreck havoc on ADRs and FP+. But there is not much to do other than roll with it, as no one can control the weather! The weather forecasters often call for 50% chance of rain every day, but that is not 50% chance it will rain all day, just at some point in the day. So don't let that discourage you either. I think May is a great time to go!