The Pacific Northwest typically experiences the most rainfall due to its maritime influence.

This region, including areas like Washington, Oregon, and northern California, is known for its temperate maritime climate. Moist air from the Pacific Ocean moves inland, where it is forced up by mountain ranges, cooling and releasing moisture as rainfall. As a result, the Pacific Northwest experiences frequent and heavy rain, particularly in the fall and winter months. The abundant rainfall, combined with mild temperatures, creates a lush environment with dense forests and diverse ecosystems, making this region one of the wettest in the United States.