This is one of the warmest and driest ecoregions in Canada. It is characterized by rolling plateaus and major valley systems of the Okanagan, Thompson and Nicola rivers. The mean annual temperature of the major valleys is approximately 6°C with a summer mean of 15°C and a winter mean of -3.5°C. Kamloops, located on the Thompson River, has the highest average daytime summer temperature of all Canadian cites at 27.2°C. The mean annual precipitation ranges 250-300 mm in the major valleys to over 1000 mm in subalpine and alpine areas. Plateau regions receive 400-600 mm. A strong gradient in precipitation occurs with elevation. Vegetative cover includes alpine, forests, and grasslands. Engelmann spruce, subalpine fir, and lodgepole pine grow in subalpine areas. Lower elevations support forests of lodgepole pine with pine grass understory, mixed with some trembling aspen, white spruce, and Douglas-fir. Valley bottoms support open stands of Douglas-fir and pine grass or parklands of scattered ponderosa pine in a matrix of bluebunch wheat grass and sagebrush. In the driest areas south of Penticton and around Kamloops, grasslands of bluebunch wheat grass, blue grass, June-grass, sagebrush, rabbitbrush, and antelope-bush occur. This ecoregion, lying within the southern section of the Interior Plateau, is composed of flat-lying Tertiary sediments and volcanic rocks 1220-1525 m asl in elevation. The region has a gently rolling surface covered mainly by glacial deposits into which rivers are commonly incised below the general surface. Glacial deposits include hummocky moraines, well-developed drumlinoid features, glaciofluvial terraces, esker complexes, and glacial lake (glaciolacustrine) deposits. The soils of the region include Humo-Ferric Podzols and Dystric Brunisols at the higher elevations, Gray Luvisols and Eutric Brunisolic soils on calcareous morainal and lacustrine deposits at middle elevations, and Eutric Brunisolic and Dark Gray Chernozemic soils at lower elevations. Dark Brown and Brown Chernozemic soils are usually associated with low-elevation valley bottoms along the Okanagan and Thompson rivers. The range of representative wildlife is equally complex and includes California bighorn sheep, mule and white-tailed deer, elk, black bear, coyote, bobcat, cougar, blue grouse, waterfowl, long-billed curlew, rattlesnake, and chukar (introduced). Land use also reflects ecological stratification. Grazing, forage production, orchards, water-oriented recreation, and residential development are common at lower elevations, woodland grazing and forestry at middle elevations, and forestry, hunting, and recreation at higher elevations. Approximately 10% of the ecoregion is farmland, much of it irrigated in horticultural or forage crops. Major communities are Penticton, Kelowna, and Kamloops. The population of the ecoregion is approximately 344 500, and growing annually as this ecoregion has become a favoured retirement area.
This ecoregion is part of the Montane Cordillera ecozone.