 The ENSO cycle has a huge effect on rainfall and snowfall patterns in California, especially during the winter and spring seasons.During the El Niño phase, the jet stream is located south through California, allowing for warmer temperatures and more heavy rains to occur, particularly in the southern portions of the state.During the La Niña phase, the jet stream is much further north, and therefore the far northern portions of California are wetter, while the southern half stays cool and dry.