The Coast and Cascade mountains influence westerly air masses flowing above the central region of Secwepemc Territory. As a result of a rain shadow effect, the vegetation located in the semi-arid valley bottoms and plateaus is drought tolerant.
Open canopies allow grasses and shrubs to dominate the undergrowth.
These dry forests provide winter habitat for large ungulates, such as mule deer, elk and bighorn sheep. Bluebunch wheatgrass is the most abundant plant species in the grasslands. Other grasses, such as fescues, needlegrasses and bluegrasses are common, as are many showy wildflowers that bloom in spring and early summer. Today, most grasslands are grazed by domestic livestock. On severely overgrazed areas, knapweed, toadflax and other weedy plants have unfortunately taken over from native species.