What ‘Very Strong’ El Niño Odds Mean for California’s Largest Reservoirs

A developing El Niño is forecast to become unusually powerful this winter, which could hold major implications for California’s water supply, reservoirs and flood risk.

The odds of a “very strong” El Niño—defined by exceptionally warm sea-surface temperatures in the equatorial Pacific—have increased dramatically as the event develops. The National Oceanic and Atmospheric Administration’s (NOAA) latest outlook, released Thursday, shows a 75 to 81 percent chance of a very strong event between November and January, the heart of California’s wet season.