Hilo has a tropical rainforest climate , with substantial rainfall throughout the year. Its location on the windward coast (relative to the trade winds), makes it the fourth-wettest city in the United States, behind the southeast Alaskan cities of Whittier, Ketchikan and Yakutat, and one of the wettest in the world. An average of around 126.72 inches (3,220 mm) of rain fell at Hilo International Airport annually between 1981 and 2010, with 272 days of the year receiving some rain. Rainfall in Hilo varies with altitude, with more at higher elevations. At some weather stations in upper Hilo the annual rainfall is above 200 inches (5,100 mm).
Monthly mean temperatures range from 71.2 °F (21.8 °C) in February to 76.4 °F (24.7 °C) in August. The highest recorded temperature was 94 °F (34 °C) on May 20, 1996, and the lowest 53 °F (12 °C) on February 21, 1962. The wettest year was 1994 with 182.81 inches (4,643.4 mm), and the driest was 1983, with 68.09 inches (1,729.5 mm). The most rainfall in one month was 50.82 inches (1,290.8 mm) in December 1954. The most rainfall in 24 hours was 27.24 inches (691.9 mm) on November 2, 2000.
Hilo’s location on the shore of the funnel-shaped Hilo Bay also makes it vulnerable to tsunamis.