Just got back from WDW. I too was stressed, bummed, anxious, etc when I saw the weather forecasts for last week. I was used to pop up quick storms but was worried about this storm system bringing all day rain. I came armed with small umbrellas, ponchos from Target, proper footwear, and hoped for the best. It was NOT as bad as feared. We had plenty of days that the sun was fully out, Times when a sprinkle passed, and some times of downpours. We survived lol. I used the accuweather app and checked it multiple times each day because it might say rain is starting in 20min but the clouds move and it’ll change to 90min and so on. Only once were we caught in a downpour as we got off of Frozen so we hung out in the gift shop (on the floor in a corner) and another night the rain changed our plans to go walk around Disney Springs. The most annoying part was soaked feet. Even in my Teva flip flops it got old fast. We used umbrellas every time, the ponchos were used also if the rain would be falling for a while. Our day at DHS, it rained for a while. We used that time to eat at backlot Express, went on star tours, and watched Indiana Jones. We even got to see Fantasmic that night.
Check accuweather the night before and again when you wake up. A lot of times the rain would start in the afternoon. Get to the parks early, get your sun-time in, get all your sunny pictures done, ride the outside rides, etc. just in case it rains or is overcast later.