Did you book through a travel agent? If so, he/she can help answer your questions about what to take, etc. You will definitely need summer clothing for Hawaii! I'd suggest wearing layers when you leave (sweater/sweatshirt, jacket, etc.) so you can peel those off when you get to tropical Hawaii, and add them when you return home. (Keep them in a carryon bag for your trip home - pack the heaviest items on top of the suitcase so you can get them out after you claim your bags on the return, and won't freeze on the way back to the car!)