A rugged and mountainous ecozone spanning 473,000 square kilometres, it still contains "two of the few significant agricultural areas of the province",[1] the Creston Valley and the Okanagan Valley.

Primarily a mountainous region, it consists of rugged ecosystems such as alpine tundra, dry sagebrush and dense conifer forests.

[3] The area has a mild climate throughout the year, with typically dry summers and wet winters.

[4] The corresponding name in the United States for this ecozone, where it is classed as a Level I ecoregion by the United States Environmental Protection Agency, which is identical though differently-named than the CEC system, is the Northwestern Forested Mountains ecoregion.

It contains the headwaters for the Fraser and Columbia rivers and many of their tributaries, notably the Thompson and Kootenay.