What is La Niña and how will it affect SoCal weather?

For the third year in a row, Southern Californians should expect yet another La Niña winter. With a 91% chance that it will arrive, another La Niña event can bring another year of drought.

During normal weather trade winds, which blow east to west, push warm surface waters towards the Eastern Pacific and Asia. In La Niña events stronger than average trade winds continue to push warm waters east, but also bring colder water to the surface. 

Typically, during a La Niña event, the weather will be drier and warmer in Southern California, while wetter and colder in areas like Northern California and Oregon. 

La Niña is one-half of the weather phenomena called the El Niño-Southern Oscillation Cycle. The other half, an El Niño, brings the opposite type of weather to Southern California. While La La Niña will bring drier and warmer climates, an El Niño will bring colder and wetter weather to Los Angeles, Orange County and the Inland Empire. 

Instances of each phenomenon can last, on average, about 9-12 months but sometimes last for years. While the phenomena are not on a set schedule they typically happen every two to seven years, with El Niños more common than La Niñas.

However, the last El Niño came in 2018. In recent memory, the strongest El Niño last arrived in 2015.