Maui is the second-largest island in the Hawaiian archipelago, at 727.2 square miles (1,883 km2). It is the 17th-largest in the United States. Maui is one of Maui County's four sizable islands, along with Molokaʻi, Lānaʻi, and Kahoʻolawe.
In 2020, Maui had a population of 168,307, the third-highest of the Hawaiian Islands, behind Oʻahu and Hawaiʻi Island. Kahului is the largest census-designated place (CDP) on the island, with a 2020 population of 28,219. It is Maui's commercial and financial hub. Wailuku is the county seat and was the third-largest CDP as of 2010. Other significant populated areas include Kīhei (including Wailea and Makena in the Kihei Town CDP), Lāhainā (including Kāʻanapali and Kapalua in the Lāhainā Town CDP), and Upcountry Maui (including Makawao, Pukalani, Kula, and Ulupalakua), although Lāhainā was mostly destroyed by fire in 2023.
Once part of Maui Nui, Maui is dominated by two volcanic features: Haleakalā in the southeast, and the West Maui Mountains in the northwest. The two are connected by an isthmus about six miles wide that gives the island its nickname, the Valley Isle.
Maui has a significant tourism industry, with nearly three million visitors in 2022. A 2023 report based on 2017 data concluded that nearly 40% of Maui County's economy was tourism-related. Popular tourist destinations include the resorts in the Kāʻanapali, Kapalua, and Kihei/Wailea/Makena areas; Hāna and the Hana Highway; ʻĪao Valley; Haleakalā National Park; and its many beaches.
Native Hawaiian tradition gives the origin of the island's name in the legend of Hawaiʻiloa, the navigator credited with discovering the Hawaiian Islands. According to that tradition, Hawaiʻiloa named the island after his son, who in turn was named for the demigod Māui. Maui's previous name was ʻIhikapalaumaewa. Maui Island is also called the "Valley Isle" for the large isthmus connecting its northwestern and southeastern volcanic masses.
Like all other Hawaiian Islands, Maui was formed from the volcanism associated with the Hawaii hotspot.
The islands' volcanic cones are formed from basalt, a dark, iron-rich/silica-poor rock, which poured out of thousands of vents as fluid lava over millions of years. Some of its volcanoes were close enough to each other that lava flows on their flanks overlapped, merging into a single island. Maui is one such "volcanic doublet," formed from two shield volcanoes that overlapped to form Maui.
The older, western volcano has eroded considerably, forming the peaks of the West Maui Mountains (in Hawaiian, Mauna Kahalawai). Puʻu Kukui is the highest, at 5,788 ft (1,764 m). The larger, younger volcano to the east, Haleakalā, rises to 10,023 ft (3,055 m) above sea level, and measures 5 mi (8 km) from seafloor to 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 isthmus was formed by sandy erosional deposits.
Maui's last eruption (originating in Haleakalā's Southwest Rift Zone) likely occurred between 1480 and 1600; the resulting lava flows are located at Cape Kīnaʻu between ʻĀhihi Bay and La Perouse Bay. Haleakalā is dormant, but not extinct.
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 200,000 years ago, the channels between them become exposed and join the island into a single landmass.
The climate is characterized by a two-season year, tropical and uniform temperatures at any given elevation, geographic differences in rainfall, high relative humidity, extensive cloud formations (except on the leeward coasts and at the highest elevations), and dominant trade wind flow (especially at lower elevations).
Maui has a range of climatic conditions and weather patterns:
Half of the land is within 5 mi (8 km) of the coast, creating a strong marine influence.
Macro weather patterns are typically determined by elevation and orientation towards the trade winds (the prevailing air flow from the northeast).
Maui's rugged, irregular topography drives variations in conditions. Air swept inland on the trade winds is redirected by the mountains, valleys, and vast open slopes. This three-dimensional flow of air produces variations in wind speed, cloud formation, and rainfall.
Maui displays diverse climatic conditions, each of which is specific to a sub-region. These sub-regions are defined by major physiographic features (such as mountains and valleys) and by location on the windward or leeward side.
Maui's daytime temperatures average between 75 °F (24 °C) and 90 °F (32 °C) year round, while evening temperatures are about 15 °F (8.3 °C) cooler in the more humid windward areas, about 18 °F (10 °C) cooler in the drier leeward areas, and cooler still in higher elevations.
An exception to the normal pattern is the occasional winter Kona storm that brings rainfall to the South and West areas accompanied by high southwesterly winds (opposite of the prevailing trade wind direction).