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Greenhouse experiments have shown that earthworms can increase wheat yields by improving nutrient cycling, water infiltration, and soil structure. However, climatic thresholds limit earthworm distribution and activity. This research aims to connect laboratory studies of earthworm environmental thresholds and impacts on wheat yield to real-world conditions in the Inland Pacific Northwest (IPNW) wheat-producing region. The European invasive species Aporrectodea trapezoides accounted for 85% of adult earthworm specimens collected, and climate plays a significant role in determining earthworm distribution, with a threshold between 350 and 400 mm of annual rainfall below which earthworms are unlikely to be present. Earthworm densities vary significantly between cropping systems and seasons, decreasing with increasing temperature and decreasing mean annual precipitation (MAP) and soil moisture. The research concludes that low densities of earthworms and limits on active periods due to environmental thresholds may limit the potential positive impact of earthworms on wheat production.