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Departures from the average number of days each winter (December–February) with an atmospheric river occurrence for (top) El Niño and (bottom) La Niña from 1992-2020. During El Niño winters, the number of days with atmospheric rivers is below average along the Alaska and western Canada coastlines, but above average along the U.S. West Coast. La Niña tends to bring the opposite: fewer atmospheric river days along the U.S.West Coast.