It is located on Haleakala's east rift zone, at the border between Hāna Forest Reserve and Haleakalā National Park.

It is alleged to be one of the wettest places on Earth, with a reported annual rainfall of 404 inches (10,300 mm)[1] for the period 1992-2018 according to the University of Hawaiʻi at Mānoa.

While the summit of Mount Waiʻaleʻale on Kauai has long been considered the wettest place in the Hawaiian Islands, and was claimed to be the second wettest place on Earth,[2] its NOAA-reported annual rainfall of 373.85 inches (9,495.8 mm)[3] is exceeded by Big Bog's 30-year average.

The Big Bog has a tropical rainforest climate (Köppen Af), with no observable dry season and nearly constant torrential rainfall.

Its reputation as the cloudiest place in the Hawaiian Islands is supported by its average solar radiation and potential evapotranspiration being the lowest amongst recorded locations in the state, and relative humidity and cloud attenuation the highest.