Pacific air loses moisture over the Cascade crest via orographic lift. Descending air over the Columbia Basin warms and dries, creating Spokane's semi-arid summer conditions.
Healthy Ponderosa pine forests act as natural hydrological pumps, recycling soil water back into atmospheric moisture plumes, lowering local temperatures, and buffering fire risk.
When relative humidity falls below 20% and temperatures rise, needle bed moisture drops. Wind vectors accelerate fire spread exponentially across contiguous canopy fuels.