There are many hikes and trails that will take you all over the islands and throughout the different climate zones. There are tropical rainforests with fruit hanging from the trees where it never seems to stop raining, there are dry desert areas that invite the rain and water but never comes. There are mountains zones that on one side the weather patterns are so completely different that it defys the imagination. Backpacking and camping in these areas are limited due to the size of the islands, but reservations made in advance should cover you.
On Hawaii there are some magnificent trails like the Crater Rim Trail in the Hawaii Volcanoes National Park, that encircles Kilauea's summit caldera closely following the path of Crater Rim Road. This is a challenging and long day hike, that passes through varied terrain, including a desert and rain forest. Views of Halemaumau and Keanakakoi Craters and Mauna Loa are excellent from this 11-mile path.
Volcanoes National Park is a goldmine of hiking trails. You'll find the Devastation Trail that leads visitors one mile over the cinder outfall and through a forest recovering from Kilauea lki's 1959 eruption. Along the path you'll find such volcanic formations as: cinder with olivine, Pele's hair and tears, tree molds and a cinder and spatter cone. The route is paved and rated as easy. A good ride for anybody with a bike
On Maui look forward to the Kaupo route that leads southward from Paliku Campground to the small town of Kaupo on the Maui coast, where fishing is reccomended. The route is nine miles one way with a very rocky surface. It is recommended that hikers do not go alone due to the rough conditions. The first three and a half miles of the route lie within the park and descend from the crater. The remainder of the route follows a jeep trail. Another winner in the realm of pure scenery department is the Pipiwai Trail in the Haleakala, it is a moderately difficult, four-mile (round trip) hike through a rain forest to Waimoku Falls. The route passes Makahiku Falls approximately one half mile from the trailhead. It ends upstream, near the base of Waimoku Falls. The clear pools formed by the smaller waterfalls along the route make excellent places to swim, although flash flooding may occur.
The island of Molokai doesn't have much in the way of proper hiking trails but there are three excellent parks that are worth visiting; The Kakahaia Wildlife Refuge, where wildlife observation and environmental education activities are available under a Special Use Permit. Picnicking and fishing are also available at the adjacent Kakahaia County Park. Kalaupapa Historic Park, has the distinction of being an area with spectacular north shore sea cliffs, narrow valleys, a volcanic crater, rain forest, lava tubes and caves, and offshore islands. Several of these areas provide rare native habitat for threatened or endangered Hawaiian plants and animals. The Pala'au State Park encompasses 233 acres of land on the northern central shore of the island. The Kalaupapa overlook provides views of the northern Molokai pali and Kalaupapa peninsula.
On the popular island of Kaua'i the Alakai Trail leads from Mohihi Road at Kawaikoi Camp in Koke'e State Park, three and a half miles to Kilohana Overlook. It passes through the northernmost portion of the Alakai Swamp. The swamp is the rainiest place on Earth, receiving nearly 400 inches of rain per year, so expect wet and slippery conditions.
Over on the middle island of Oahu is the Manoa Falls Trail that leads one mile into the Honolulu Watershed Forest Reserve. It begins on Manoa Road above the Lyon Arboretum. Most of the trail follows Waihi Stream, which forms the falls and feed the lush forest around it. A few switchbacks and a set of stairs puts hikers above the stream at the falls. Immediately before reaching the falls Manoa Falls Trail intersects the Aihualama Trail. A shallow pool lies beneath Manoa Falls, but swimming is not advised due to frequently falling rock. The state parks are excellent resources for trails and the like.