This ecoregion is a mountainous upland region within the eastern portion of the southern Pacific Ranges. The ecoregion incorporates a strong climatic gradient from the moist maritime climate of the coast to the semiarid continental climate of the southern interior of British Columbia. Elevation ranges 300-3000 m asl. The mean annual temperature for the area is approximately 6°C with a summer mean of 15°C and a winter mean of -3.5°C. The mean annual precipitation experiences a strong gradient through the Fraser Canyon ranging from south (300 mm) to north (500 mm) and in the mountain ranges from west (1200 mm) to east (800 mm). This ecoregion contains ecosystems ranging from alpine at the highest elevations; to subalpine forests of Engelmann spruce, alpine fir, and lodgepole pine; and to montane forests of lodgepole pine, trembling aspen, white spruce, and Douglas-fir. At the lowest elevations in the eastern portions of the ecoregion there is a parkland of scattered ponderosa pine in a matrix of bluebunch wheat grass and sagebrush grasslands. The soils of the region vary from Humo-Ferric Podzols and Dystric Brunisols at the higher elevations, to Gray Luvisols and Eutric Brunisolic soils on calcareous morainal and lacustrine deposits at middle elevations, and to Eutric Brunisolic and Dark Gray Chernozemic soils at lower elevations. Dark Brown and Brown Chernozemic soils are usually associated with valley bottoms along the lower Fraser River and its tributaries. Characteristic wildlife are mule deer, bighorn sheep, mountain goat, grizzly and black bear, cougar, coyote, grouse, and various raptors. Land uses reflect high recreational and wildlife values in alpine and subalpine zones, whereas forestry and agriculture tend to become more important in lower, warmer zones. Mineral exploration occurs throughout the region. There are 50 000 ha of farmland in the ecoregion, the most productive are the irrigated forages, mainly alfalfa, on the benchs of the Fraser and lower Thompson rivers. These river valleys are also important transportation corridors. The main communities are Lillooet and Lytton. The population of the ecoregion is approximately 6900.
This ecoregion is part of the Montane Cordillera ecozone.