Our motto is "keep calm and poncho on".
This way you're not getting wet, running, feeling rushed, feeling like you can't do anything, getting upset when others are oblivious that you're trying to get past them etc.
My sister and I wore a poncho from 9:15am to 3:15pm last time we were in MK.
We use fairly durable throw aways that have sleeves and a drawstring so we brought a few into the park and wore one until we went to lunch and then wore another until we left the park for a break.