I would bring a little of everything! Our first day last December (the 8th I believe) it was rainey and cold. Day two was warmer but we still wore jackets. Day three was quite toasty and we left the parks early and swam! My 80 year old stepdad had not brought his swimsuit because hey, it was December! So I offered to buy one for him in DTD (he rode the monorail back to the DLH with my mom) and he could reimburse me. Well it was like $75 to buy a suit! I knew with him being a child of the depression he would never pay that much so I lied and told him it was only $20! He wore that suit recently and said what nice suit it was for only $20. Bring your jackets, jeans, shorts and a swimsuit and be prepared to change your seasonal wear daily!