The beaches around the islands are usually at a comfortable range of temperatures throughout the year. The average water temperature at the mid 70s to low 80s help beachgoers stay in the water and enjoy water sports all day. However, the waves depend on the movement of the Pacific Ocean and during storms, the waves rise to dangerous levels. Anyone participating in a beach activity, especially those with families and little children should keep an eye out for warnings and listen to the life guards and coast guards at all times.
The temperature over the mountains are naturally cooler than that of the beaches and people should dress appropriately when going on tours and hiking. The summit of the Haleakala can be as much as 30 degrees cooler than the coastal temperature.
Sunscreen, Hats, sun glasses, jackets, water bottles, etc are essential for travelers, and everything is available in Hawaii at its many supermarkets.