Kukui Hawaii is the highest peak of Mauna Kahalawa (the West Maui Mountains) and came to be when a crater formed by a volcanic collapse created the I’ao Valley below. With 9,239 mm of rainfall a year, it is the third wettest place in Hawaii. Puʻu Kukui is one of the wettest spots on Earth and the third wettest in the state after Big Bog, Maui and Mount Waiʻaleʻale, receiving an average of 386.5 inches (9,820 mm) of rain a year. Rainwater unable to drain away flows into a bog.