Temperate rainforests are coniferous or broadleaf forests that occur in the mid-latitudes in areas of high rainfall. Most of these occur in Oceanic-Moist Climates in Western North America (Southeastern Alaska to Central California), Western Europe (Southern Norway to Northern Spain), Southwestern South America (Southern Chile), Southeastern Australia (Tasmania/Victoria), and Western New Zealand (South Island's west coast). Others occur in Subtropical-Moist Climates (The Colchian temperate rain forests of the Eastern Black Sea region of Turkey and Georgia, New Zealand's North Island, South Africa's Garden Route, Western Japan, and the mountain temperate coniferous rain forests of Taiwan's Central Mountain Ranges). Some areas, however, such as the Russian Far East (Ussuri, Manchuria, Sakhalin) in Asia, British Columbia's Rocky Mountains, Cariboo Mountains, Rocky Mountain Trench (east of Prince George) and the Columbia Mountains of BC's interior, and in the Appalachian Mountains of Eastern North America have more of a continental climate but get enough precipitation in both rain and snow to harbor pockets of temperate rain forest. The mountainous coniferous forests of the Changbai Mountains bordering China and North Korea are a good example contain some of the richest high-elevation coniferous evergreen forests in Eastern Asia. Temperate rain forests are distinguished from other temperate forests by a few factors:

• Rainfall: high rainfall (minimum 2-3 m/year, depending on latitude), usually from moisture-laden winds off the ocean.
• Relative proximity to the ocean: temperate rain forests depend on the proximity to the ocean to moderate seasonal variations in temperature, creating milder winters and cooler summers than continental-climate areas. Many temperate rain forests have summer fogs that keep the forests cool and moist in the hottest months.
• Coastal mountains: temperate rain forests occur where mountain ranges are close to the coast; coastal mountains increase rainfall on the ocean-facing slopes.
• Inland rainforests (including some of the richest and most diverse sites in the world) also occur along British Columbia's Rocky Mountain Trench, east and southeast of the city of Prince George. The Interior Cedar Hemlock (ICH) zone in the Rocky Mountain Trench east of Prince George is of particular significance with respect to climate change. Climatic warming projections suggest that by mid century or soon afterwards, this location may be at the southerly extent of the ICH. The ICH zone will also have spread throughout much of the Prince George area and farther north, but of course there will not be ancient forests for many hundreds or thousands of years, if ever. The Rocky Mountain Trench east of Prince George therefore offers the last best chance to preserve some of the globally rare 'Tier-1' ICH sites.

Temperate rain forests may be predominantly coniferous (with deciduous trees in understory), broadleaf evergreen, or mixed forests with deciduous species, and occur in Temperate broadleaf and mixed forests and Temperate coniferous forests ecoregions.

The temperate coniferous rain forests sustain the highest levels of biomass in any terrestrial ecosystem and are notable for trees of massive proportions, including Coast Redwood (Sequoia sempervirens), Coast Douglas-fir (Pseudotsuga menziesii), Sitka Spruce (Picea sitchensis), Alerce (Fitzroya cupressoides) and Kauri (Agathis australis). These forests are quite rare, occurring in small areas of Western North America, southwestern South America and northern New Zealand.

Temperate forests cover a large part of the globe, but temperate rain forests only occur in seven regions around the world; the Pacific temperate rain forests of North America, the Valdivian and Magellanic temperate rain forests of southwestern South America, the Colchian rain forests of the eastern Black Sea region (Turkey and Georgia), the New Zealand temperate rain forests, Tasmanian temperate rain forests, South Africa's Knysna-Amatole coastal forests, and pockets of rain forest in northwest Europe and southwest Japan's Taiheiyo evergreen forests. Also, there are forests similar to those in Japan in Taiwan's Montane forests of the Central Mountain Ranges along Eastern Taiwan's Pacific Coast. Scattered small pockets of temperate rain forest also exist along the Appalachian Mountains from northern Georgia to New England, British Columbia's Columbia Mountains, and in parts of Sakhalin Island, Manchuria and the Ussuri Region of the Russian Far East in Asia.