We quantified the relationship between atmospheric rivers (ARs) and occurrence and magnitude of extreme precipitation in western U.S. watersheds, using ARs identified by the Atmospheric River Tracking Method Intercomparison Project and precipitation from a high‐resolution regional climate simulation. Our analysis shows the potential of ARs in predicting extreme precipitation events at a daily scale, with Gilbert Skill Scores of ~0.2. Monthly extreme precipitation amount in west coast watersheds is closely related to AR intensity, with correlation coefficients of up to 0.6. The relationship between ARs and precipitation is most significant in the Pacific Northwest and California. Using a K‐means clustering algorithm, ARs can be classified into three categories: weak ARs, flash ARs, and prolonged ARs. Flash ARs and prolonged ARs, though accounting for less than 50% of total AR events, are more important in controlling extreme precipitation patterns and should be prioritized for future studies of hydrological extreme events.