In 2021, a historic drought that affected much of the western United States led to reduced water supply and, as a result, lower hydropower generation in the Pacific Northwest and California. Electricity generation at California’s hydropower plants last year was 48% below the 10-year average (2011–2020). In the Pacific Northwest, which consists of Washington, Oregon, Montana, and Idaho, hydropower generation was 14% below the 10-year average.