The topography of the Thompson Okanagan region is extremely varied.
To the north is the highest mountain in the Canadian Rockies; to the south is a desert environment; in between is a rich valley that produces more orchard fruit and wine than any other region in BC. In fact, the Okanagan is one of the few areas in Canada where apples and "soft fruit" such as peaches and apricots can be grown.
The fruit- and wine-producing Okanagan Valley stretches 200km/124mi between the Cascade Mountains to the west and the Monashee Mountains to the east. A network of lakes and rivers stir air currents in the valley, creating mild winters in the south and frigid winters in the north. A true desert climate (the only one in Canada) exists at the Okanagan Valley's southern tip in and around the town of Osoyoos. Elevations in the Okanagan range from 275m/902ft at Osoyoos Lake to 2,304m/7,559ft at Mount Baldy.
The southwestern portion of the region is the Similkameen Valley. It is bounded by the Cascade Mountains to the west and the Okanagan Range to the east. There are desert-like grasslands at the bottom of this valley that are bordered on one side by marshland and cottonwood/birch woodland.
The Thompson-Nicola area lies mainly within the Southern Interior Plateau and is defined, for the most part, by the Thompson River. It stretches from the North Continental Range of the Rocky Mountains in the north to ranches and historical gold rush towns in the south. This area is hot in summer and cold in winter. Most of its precipitation occurs in the mountains. Mount Robson is the highest peak in the Canadian Rockies.