LIVE: Track Bay Area weather conditions
La Niña is when ocean waters off the coast of South America in the Pacific are cooler than average. La Niña typically sends the jet stream, a fast-moving current of air thousands of feet in the atmosphere, which acts as a highway for storms far north over the Pacific Northwest.
While no two La Niña winters are exactly the same, odds are this will bring average to below average rainfall across the Bay Area this winter.