Hawaii is perfect any time of the year, but, if you're going to spend any time in the Southern California area, keep in mind that July, August, and September can be unbearably hot. Plus, these months tend to be more expensive in both California and Hawaii. We went over Christmas and New Years and had lovely sunny days in California with temperatures around 20-21 and even lovelier days in Hawaii with temperatures around 24-26.
Hawaii is great to visit at any time of the year. Personally we would avoid going there in the American holiday season as the islands tend to pretty full during these times. Neil and Ida Dow.