I recommend either thinking about a locker, a backpack, or things you can tie around waist instead of carrying them as you shed layers during the day. If you buy a cute short sleeve T shirt, consider buying it large enough to wear a snug long sleeve T under it if needed. A PP mentioned leggings... some of those can be quite light weight and you may want more than that. I have worn thin long underwear under jeans a few times in December at Disney and on the same trip worn shorts and gone to the pool. As everyone has said, you have to be prepared for a wide range of temps. Now, of course, when it gets cold quickly, Disney is happy to clearly display additional racks of sweatshirts, fleece jackets, lounge pants, and winter hats and watch the money pour in. I think I own four Disney winter scarves now due to my own attire mistakes.