In Hawaii, as a rule, one should wear cool, cotton casual clothing and comfortable shoes appropriate for activity plans. It's a good idea to bring a hat because the tropical Hawaiian sun is often intense. Shorts are often acceptable even in professional settings, and Hawaiian aloha wear is acceptable everywhere.
Hawaiian culture overall is laid-back and casual, designed around a largely outdoor lifestyle and a tropical climate. Swim gear is a must, as are sturdy comfortable shoes. A polo shirt and slacks or shorts are typical wear for a man, and women usually wear cool tops with shorts, lightweight pants or skirts.
Aloha clothing, featuring colorful, tropical cotton or linen prints and loose, comfortable designs, is a Hawaiian staple. Examples of aloha clothing for women include loose, waistless dresses called muumuus and sarongs wrapped and tied in a variety of styles. Men and women both wear aloha shirts, called "Hawaiian shirts" by most mainlanders.
In evenings near or on the ocean and at altitudes, temperatures can drop surprisingly low. In fact, at the peak of Hawaii's highest mountain, Mauna Loa, there is often snow. For this reason, it's a good idea to pack at least one pair of jeans or pants as well as a sweater. When planning a full day of activity in a variety of locations, one should dress in light layers.