The sub-regions are in rain shadows from the Cascade or Sierra Nevada ranges that block precipitation from Pacific storms.

North American Monsoon storms can occur in the region during the mid-summer, coming northeast from the Pacific Ocean and Mexican Plateau.

Intermountain West ecoregions include: Some sections are agriculturally cultivated with water diversions for irrigation systems.

The 18th-century fur trade (northern areas), and 19th-century westward expansion of the United States brought irreversible cultural changes.

Historically, the Intermountain West area centered in Utah is associated with Latter-day Saint (Mormon) settlements, and the region has the highest percentage of LDS members in the United States currently.