We went in January 2001 to US (no wet rides to worry about). What I remember -
It was nice during the middle of the day, but in the a.m. and afternoon we needed sweatshirts.
It was smoky - there was a fire somewhere nearby - a few miles away it was a beautiful clear day, but in the parks it looked overcast from the smoke.
There were NO crowds - everything was a walk-on, except MIB, which had about a 10-15 min. wait time. After our first time, we just went back through the single rider lines (about 5 or 6 more times - love that ride!!). Keep in mind, we were there the third Saturday of the month, so the holiday crowd had died down significantly. I think you'll have more crowds the closer to the holidays you are.
The park did close early, but since there were no crowds, we were able to do everything we wanted.