How did the Plateau region's rain shadow affect its climate and vegetation?

The mountain systems surrounding the Plateau region act as an orographic barrier to moisture-laden air, creating a significant rain shadow effect. As Pacific storms move inland, they deposit the majority of their precipitation on the windward, western slopes of the coastal mountain ranges and the Cascades.12

This process leaves the interior Plateau region relatively dry, as most moisture is blocked before reaching it. Consequently, the region experiences low annual precipitation, which contributes to its distinct climate and vegetation patterns:123

• Climate: The region features a continental climate with significant temperature fluctuations, ranging from extreme winter lows to hot summer highs. Because the surrounding mountains provide protection from continental air masses, the climate is generally temperate, though drier than the adjacent Plains.31
• Vegetation: The limited rainfall supports three primary vegetation provinces. The Middle Columbia area is characterized by a steppe of sagebrush and bunchgrass, while the Upper Columbia consists of wooded areas and river valley grasslands. The Fraser area features semi-open coniferous forests mixed with dry grasslands. Overall, the region is dominated by grassland and high desert ecosystems, with more substantial forests found only at higher altitudes where precipitation is more frequent.31