In Southern California, it can be hot during the day and still get chilly at night. It may be mid 80s at 3pm and mid 50s at 10 pm. I would reccomend you take the sweater and a pair of jeans/pants to change into.
Also, they pump up the AC in several attractions. If you usually run warm, you should be fine. But I usually run a little cool and I FREEZE in space mountain, pirates, and haunted mansion. So keep your own temperature preferences in mind as well.
I just checked weather.com. At this point it looks like it will be mid 70s on the 10th.
I live in AZ and I love to say that it is the only place where you need to go outside to get warm. What is it with the A/C cranked up so hi. My hubby likes to say that I freeze in 100 degree weather. Considering it gets over 100 here I think he's right.
I also freeze on those rides too.