I would say yes, look at a weather app, rain all week. Earlier today all the outside attractions at the MK were showing as closed in MDE, this is normally due to storms and lightning in the area. This is the time of year we go (will be there next week) and it is always stormy (and I mean absolute downpours, like Noah and the Ark downpours). It does stop, but it can always start up again. Invest in decent ponchos and go with it! Not much else you can do.
In Central Florida, the thunder and rain usually last around 15 minutes. It’s “splash and dash” as they call it here. Hard to predict as well. If you’re in Magic Kingdom, plan to focus on the indoor attractions and find a place ahead of time to dine indoors like a table service or indoor quick service restaurant.