The temperate rainforest is a unique biome defined by consistently high rainfall and mild temperatures throughout the year. This ecosystem thrives in coastal regions that receive between 60 and 200 inches of precipitation annually, often supplemented by heavy coastal fog. Unlike tropical rainforests, these forests experience distinct seasons, though temperatures rarely drop below freezing or rise above 80°F. This environment supports towering coniferous trees and a high density of plant life, particularly mosses and ferns, creating a lush green landscape. The largest US examples are found along the Pacific Northwest coast.
Washington State: The Primary Temperate Rainforest Destination
Washington State hosts accessible and pristine examples of this ecosystem, primarily within Olympic National Park. The Olympic Peninsula’s western slopes intercept moisture-laden air from the Pacific Ocean, which is forced upward by the Olympic Mountains. This orographic lift causes the air to cool and release massive amounts of water, resulting in rainfall that can exceed 140 to 167 inches annually.
The park contains several distinct rainforest valleys open to visitors, including the Hoh, Quinault, Queets, and Bogachiel. These valleys are dominated by huge conifers, such as the Sitka spruce and Western hemlock, which grow to immense sizes. Mosses and ferns heavily drape the branches of bigleaf maples and Douglas firs, demonstrating the abundance of epiphytes.
The forest floor features slow decomposition, allowing fallen trees to become “nurse logs.” These decaying trunks provide a moist substrate for new seedlings to germinate. When the original log rots away, the new trees are left standing on stilt-like roots, a signature feature of this ecosystem. The lush understory also supports the Roosevelt elk, the largest subspecies of elk in North America.
Temperate Rainforests in Other US States
Beyond Washington, the Pacific temperate rainforest ecoregion extends northward into Alaska and southward into Oregon and California. Alaska holds the largest expanse of this biome in the world within the Tongass National Forest. This national forest covers nearly 17 million acres, encompassing islands, deep fjords, and coastal mountains in the state’s panhandle.
The Tongass represents a remote, northern temperate rainforest where the landscape transitions into areas of muskeg, glaciers, and alpine tundra. Its ecosystem is dominated by towering Sitka spruce and Western hemlock, many of which are centuries old. This forest supports extensive populations of brown and black bears, bald eagles, and all five species of Pacific salmon.
Moving south, the temperate rainforest becomes more fragmented but is present along the coasts of Oregon and Northern California. The southern extent in California is known as the “coast redwood zone.” Redwood National and State Parks protect the world’s tallest trees, which rely heavily on coastal fog and high moisture levels for survival. These southern pockets still showcase the characteristic enormous trees and dense, water-dependent flora.
What to Expect When Visiting
A trip into a temperate rainforest requires preparation for a world dominated by water and muted light. The climate features constant high humidity and frequent precipitation, often manifesting as persistent mist or drizzle. Temperatures are mild year-round, so visitors should expect a damp atmosphere with moderate air temperatures.
The forest floor is often spongy and saturated. Practical preparation should include layered clothing and reliable waterproof outer layers, including sturdy, water-resistant footwear. This gear is necessary to comfortably navigate the frequently wet trails and boardwalks.
Visitors will experience an overwhelming sense of green, with nearly every surface—from tree trunks to fallen branches—blanketed in vibrant mosses and liverworts. Unique forms of fungi thrive in the perpetually damp, decomposing wood. While sightings of large mammals, such as elk, may occur, the spectacle is the sheer biomass and density of the ancient plant life.