Hoh Glacier lies on Mount Olympus in Olympic National Park in Washington and forms the source of the Hoh River. At 3.06 miles long, it is the mountain’s longest glacier, though it holds less ice by volume than Blue Glacier. It sits within the marine west coast climate zone of western North America, where Pacific weather systems rise over the Olympic Mountains and produce heavy precipitation. In winter, that moisture commonly falls as rain or snow under cloudy skies, while summer usually brings clearer weather as high-pressure systems over the Pacific strengthen.