Hawaii is a year-round destination and sees on average about nine million visitors annually. Being in the tropics, Hawaii has a “wet season” (November-March) and a “dry season” (June-September) but do take these lightly as it doesn’t rain all the time in the wet season and the sun is constantly shining during the drier months. Every Hawaiian island also has its microclimates which greatly affect local weather patterns. Further reading: How to Plan a Trip to Hawaii Like a Pro.
Each Hawaiian island has its distinct vibe and pros and cons. Head to Molokai for authenticity, laid-back vibe, off-the-grid feel, and hiking. Hop to the Big Island for hiking, long road trips, snorkeling, the active volcano, and family-friendly options. Head to Maui for its plentiful beach and resort options, scenic drives, diverse geology, and snorkeling. Skip over to Kauai for its majestic tropical scenery, hiking, scenic drives, off-the-radar beaches, and family-friendly resorts. On Oahu, enjoy its beaches, shopping scene, road trips, superb hiking, and history. Further reading: The Best Islands in Hawaii.
If you’re planning a trip to Hawaii for the resort experience and with little reason to hop to other islands, there is really no rule of thumb. You could visit for a long weekend or even spend a whole week just on one island. If planning a proper island-hopping trip in Hawaii, my rule of thumb is that for every week in Hawaii, you can explore a maximum of two islands. Three nights on an island is really the minimum. Further reading: 7-Day Sample Itinerary, Two-Week Sample Itinerary.
Unless you charter a yacht or plane, commercial inter-island flights are the only practical means of getting from one island to another in Hawaii.
Oahu: Pearl Harbor, Diamond Head, Hanauma Bay, Makapu‘u Point, north shore
Maui: Haleakala National Park, the road to Hana, Kahekili Highway scenic drive, Molokini Crater
Kauai: Waimea Canyon, Kalalau Trail, Na Pali coast, Hanalei Bay
Big Island: Kona coast beaches, Waipi’o Valley, Volcanoes National Park, sunset at Mauna Kea
Molokai: Kalaupapa National Historical Park, Halawa Valley, Molokai’s cloud forest
Further reading: Top Things to Do in Hawaii.