The island of Maui is the second-largest of the Hawaiian Islands just under 730 square miles and is the 17th largest island in the United States. Maui is part of the State of Hawaii and is the largest of Maui County’s four islands, which include Molokaʻi, Lānaʻi, and unpopulated Kahoʻolawe. In 2020, Maui had a population of 167,417, the third-highest of the Hawaiian Islands. Kahului is the largest census-designated place on the island with a population of 31,336 as of 2020 and is the commercial and financial hub of the island. Wailuku is the seat of Maui County and is the third-largest census-designated place as of 2020. Other significant places include Kīhei (including Wailea and Makena in Kihei Town, the island’s second-most-populated area), Lāhainā (including Kāʻanapali and Kapalua in the Lāhainā Town), Makawao, Pukalani, Pāʻia, Kula, Haʻikū, and Hāna.
Native Hawaiian tradition gives the origin of the island’s name in the legend of Hawaiʻiloa, the navigator credited with the discovery of the Hawaiian Islands. According to it, Hawaiʻiloa named the island after his son, who in turn was named for the demigod Māui. The earlier name of Maui was ʻIhikapalaumaewa. The Island of Maui is also called the “Valley Isle” for the large isthmus separating its northwestern and southeastern volcanic masses.
Maui’s diverse landscapes are the result of a unique combination of geology, topography, and climate. Each volcanic cone in the chain of the Hawaiian Islands is built of dark, iron-rich/quartz-poor rocks, which poured out of thousands of vents as highly fluid lava over a period of millions of years. Several of the volcanoes were close enough to each other that lava flows on their flanks overlapped one another, merging into a single island. Maui is such a “volcanic doublet,” formed from two shield volcanoes that overlapped one another to form an isthmus between them.
The older, western volcano has been eroded considerably and is cut by numerous drainages, forming the peaks of the West Maui Mountains (in Hawaiian, Mauna Kahalawai). Puʻu Kukui is the highest of the peaks at 5,788 feet. The larger, younger volcano to the east, Haleakalā, rises to more than 10,000 feet above sea level and measures 5 miles from the seafloor to the summit.
The eastern flanks of both volcanoes are cut by deeply incised valleys and steep-sided ravines that run downslope to the rocky, windswept shoreline. The valley-like Isthmus of Maui that separates the two volcanic masses was formed by sandy erosional deposits.
Maui’s last eruption (originating in Haleakalā’s Southwest Rift Zone) occurred around 1790; two of the resulting lava flows are located (1) at Cape Kīnaʻu between ʻĀhihi Bay and La Perouse Bay on the southwest shore of East Maui, and (2) at Makaluapuna Point on Honokahua Bay on the northwest shore of West Maui. Considered to be dormant by volcanologists, Haleakalā is certainly capable of further eruptions.
Maui is part of a much larger unit, Maui Nui, that includes the islands of Lānaʻi, Kahoʻolawe, Molokaʻi, and the now submerged Penguin Bank. During periods of reduced sea level, including as recently as 20,000 years ago, they are joined together as a single island due to the shallowness of the channels between them.
The climate of the Hawaiian Islands is characterized by a two-season year, tropical and uniform temperatures everywhere (except at high elevations), marked geographic differences in rainfall, high relative humidity, extensive cloud formations (except on the driest coasts and at high elevations), and dominant trade-wind flow (especially at elevations below a few thousand feet). Maui itself has a wide range of climatic conditions and weather patterns that are influenced by several different factors in the physical environment:
- Half of Maui is situated within 5 miles of the island’s coastline. This and the extreme insularity of the Hawaiian Islands account for the strong marine influence on Maui’s climate.
- Gross weather patterns are typically determined by elevation and orientation towards the Trade winds (prevailing airflow comes from the northeast).
- Maui’s rugged, irregular topography produces marked variations in conditions. Air swept inland on the Trade winds is shunted one way or another by the mountains, valleys, and vast open slopes. This complex three-dimensional flow of air results in striking variations in wind speed, cloud formation, and rainfall.
Maui displays a unique and diverse set of climatic conditions, each of which is specific to a loosely defined sub-region of the island. These sub-regions are defined by major physiographic features (such as mountains and valleys) and by location on the windward or leeward side of the island.
- Windward lowlands – Below 2,000 feet on north-to-northeast sides of an island. Roughly perpendicular to the direction of prevailing trade winds. Moderately rainy; frequent trade wind-induced showers. Skies are often cloudy to partly cloudy. Air temperatures are more uniform (and mild) than those of other regions.
- Leeward lowlands – Daytime temperatures are a little higher and nighttime temperatures are lower than in windward locations. Dry weather is prevalent, with the exception of sporadic showers that drift over the mountains to windward and during short-duration storms.
- Interior lowlands – Intermediate conditions, often sharing characteristics of other lowland sub-regions. Occasionally experience intense local afternoon showers from well-developed clouds that formed due to local daytime heating.
- Leeward side high-altitude mountain slopes with high rainfall – Extensive cloud cover and rainfall all year long. Mild temperatures are prevalent, but humidity is higher than in any other sub-region.
- Leeward side lower mountain slopes – Rainfall is higher than on the adjacent leeward lowlands but much less than at similar altitudes on the windward side; however, maximum rainfall usually occurs leeward of the crests of lower mountains. Temperatures are higher than on the rainy slopes of the windward sides of mountains; cloud cover is almost as extensive.
- High mountains – Above about 5,000 feet on Haleakalā, rainfall decreases rapidly with elevation. Relative humidity may be ten percent or less. The lowest temperatures in the state are experienced in this region: air temperatures below freezing are common.
Maui is a leading whale-watching center in the Hawaiian Islands due to humpback whales wintering in the sheltered ʻAuʻau Channel between the islands of Maui county. The whales migrate approximately 3,500 miles from Alaskan waters each autumn and spend the winter months mating and birthing in the warm waters off Maui, with most leaving by the end of April. The whales are typically sighted in pods: small groups of several adults, or groups of a mother, her calf, and a few suitors. Humpbacks are an endangered species protected by U.S. federal and Hawaiʻi state law. There are estimated to be about 22,000 humpbacks in the North Pacific. Although Maui’s Humpback faces many dangers, due to pollution, high-speed commercial vessels, and military sonar testing, their numbers have increased rapidly in recent years, estimated at 7% growth per year.
Maui is home to a large rainforest on the northeastern flanks of Haleakalā, which serves as the drainage basin for the rest of the island. The extremely difficult terrain has prevented exploitation of much of the forest.
Agricultural and coastal industrial land use has had an adverse effect on much of Maui’s coastal regions. Many of Maui’s extraordinary coral reefs have been damaged by pollution, run-off, and tourism, although finding sea turtles, dolphins, and Hawaii’s celebrated tropical fish, is still common. Leeward Maui used to boast a vibrant dry ‘cloud forest’ as well but this was destroyed by human activities over the last three hundred years.
The birdlife of Maui lacks the high concentration of endemic birdlife found in some other Hawaiian islands, as recently as 200,000 years ago it was linked to the neighboring islands of Molokai, Lanai and Kaho’olawe in a large island called Maui Nui, thus reducing the chance of species endemic to any single one of these. Although Molokai does have several endemic species of birds, some extinct and some not, in modern times Maui, Lanai and Kaho’olawe have not had much endemic birdlife. In ancient times during and after the period in which Maui was part of Maui Nui, Maui boasted a species of moa-nalo (which was also found on Molokai, Lanai and Kaho’olawe), a species of harrier (the Wood harrier, shared with Molokai), an undescribed sea eagle (Maui only), and three species of ground-dwelling flightless ibis (Apteribis sp.), plus a host of other species. Today, the most notable non-extinct endemics of Maui are probably the ‘Akohekohe (Palmeria dolei) and the Maui parrotbill (Pseudonestor xanthophrys), both of which are critically endangered and only found in alpine forest on the windward slopes of Haleakala. Birds found on other islands as well as Maui include the I’iwi (Drepanis coccinea], ‘Apapane (Himatione sanguinea), as well as the Nene (Branta sandvicensis, the state bird of Hawaii), Hawaiian coot (Fulica alai), and a number of others.