El Niño conditions — the warming of ocean waters off South America that can alter weather across the globe, including California’s summer temperatures and the amount of rain it might receive next winter — are emerging in the Pacific Ocean for the first time in 4 years.

While El Niños do not automatically guarantee wet weather for California, historically, the stronger they are, the more likely it is that the state will have a rainy winter season. And after the dramatic series of storms this past winter that ended the drought and filled nearly empty reservoirs, another one back-to-back could increase flood risks.