Hawaii is, for the most part, a casual beach destination. Shorts and sandals (or good walking shoes) are good daytime fare. Also be sure to take a good pair of sunglasses and a wide brimmed hat for protection from all that sunshine. And, of course, don’t forget your swimsuit!
As the sun sets, casual shirts and pants, for both men and women, is normal dress. And dresses or skirts and blouses are also good choices for the girls. If you are going to an upscale restaurant, sport coats are acceptable. And always remember to have a shawl, sweater or jacket of an evening. It can get a little cool after dark, especially if you are on or near the water.
If you will be going to higher elevations, it can get very cold and you will want a heavier coat or sweatshirts. Good hiking shoes are a must if you are planning on being active while in the islands.
Also, a small umbrella will be handy for those quick showers that pop up intermittently during the day. I like the ones that fit in my purse.
In general, “casual” is the word of the day in Hawaii, so pack light and enjoy your Hawaii vacation!