A few years ago when we went in mid-November, the forecast showed some nights with lows in the 40s, so we brought sweatshirts, jeans and jackets for everybody. We were driving, and I assumed we wouldn't need them. If we were flying, we probably would have left the warm clothes at home.
Boy did we need them!! In an 8-day trip, we had four days that were pretty cold, with one of those where the high was only 44. We were at Animal Kingdom for the high-44 day, and it was EMPTY. We hit Everest around 10 am and still had it all to ourselves - I remember people walking out as we got there, and they looked like they came out of a freezer. Kali was operating, and we watched a few rafts that just had two pre-teen boys each; we did not ride it. Maharajah was open, but there were almost no animals outside. We also had a day at MK where the high was around 60, but the morning was mid-40s and rainy, and it was a party night. So MK pretty much stayed empty from 9-7, and we stayed the whole time. I remember Dumbo was only operating one side at 5 pm, and it was still running half-full.
Ultimately, we enjoyed all of the cooler days, mostly because it reduced the crowds, but we had to change our plans somewhat and rely on our heavier clothes. We were reminded that being outside for many hours at a time, with lots of water around, and sometimes going on fast outdoor rides, makes your body gradually feel colder and colder.
Incidentally, the other days on the trip were fairly warm, with two days in the mid-80s.