{"id":6840,"date":"2026-08-15T07:06:29","date_gmt":"2026-08-15T07:06:29","guid":{"rendered":"https:\/\/nextcitydigest.com\/?p=6840"},"modified":"2026-08-15T07:06:29","modified_gmt":"2026-08-15T07:06:29","slug":"el-nino-continues-to-strengthen-what-does-that-mean-for-flood-risk-this-winter","status":"publish","type":"post","link":"https:\/\/nextcitydigest.com\/?p=6840","title":{"rendered":"El Ni\u00f1o continues to strengthen. What does that mean for flood risk this winter?"},"content":{"rendered":"

The already strong El Ni\u00f1o conditions in the Pacific Ocean continue to grow stronger, federal scientists said Thursday, with a 69% chance that this year\u2019s event will be the strongest since modern records began in 1950.<\/p>

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Scientists at the National Oceanic and Atmospheric Administration in College Park, Maryland announced there is a 90% chance of a very strong El Ni\u00f1o through this fall and winter as water temperatures along the equator off South America continue to rise.<\/p>\n

But while El Ni\u00f1o increases the odds of wet winters in California, it doesn\u2019t mean what many people assume: That flooding is imminent later in the year for residents who live along rivers and creeks.<\/p>\n

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\"Top<\/figure>\nOf the 10 worst flooding years in California since 1950, ranked by dollar damage compiled by the California Office of Emergency Services, only three came during El Ni\u00f1o years.<\/p>\n

Most of the worst \u2014 like in 2017, when downtown San Jose suffered $100 million in damage after Coyote Creek surged over its banks and 188,000 people were evacuated in the Sacramento Valley when the spillway at Oroville Dam collapsed \u2014 came when no El Ni\u00f1o conditions were present.<\/p>\n

The reason? What matters most is not the total amount of rainfall in a year, experts say, but when it falls.<\/p>\n

\u201cTiming is everything,\u201d said Jan Null, a meteorologist with Golden Gate Weather Services in Half Moon Bay who compiled 76 years of data on the pattern.<\/p>\n

\u201cSome people think there is a 1-to-1 relationship,\u201d he said. \u201cPeople equate El Ni\u00f1o with flooding in California. But that\u2019s not always the case. Most of the worst flooding years weren\u2019t El Ni\u00f1o years.\u201d<\/p>

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When wet weather arrives, it takes time for watersheds surrounding lakes, rivers, and creeks to saturate and produce significant runoff. Water levels rise.<\/p>\n

If storms are spread out, rivers and creeks have time to recede when the rain stops. But if several big storms come back-to-back-to-back, they continue to rise, and flooding occurs.<\/p>\n

There have been four winters since 1950 with very strong El Ni\u00f1o conditions like this year. In 1982-83 and 1997-98, the Bay Area, Southern California and much of the state experienced double their average annual rainfall, with regular downpours and some flooding.<\/p>\n

In another, 1991-92, the Bay Area was relatively dry, with 84% of normal rainfall, while Southern California was wet, with 133% and no major flooding in either area. And in the most recent \u2014 2015-16 \u2014 the Bay Area had an average winter, and Southern California was drier than normal. Despite the event being heralded for months as a \u201cGodzilla El Ni\u00f1o,\u201d it was largely a bust, failing to end a prolonged drought.<\/p>

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Null cites 1997-98 as the classic example of why storm timing matters. That year, San Francisco was drenched with its second-wettest winter in history dating back to 1849, receiving 47 inches of rain, double its historical average. Other California cities received similar deluges. But flooding damage statewide was modest.<\/p>\n

That winter ranked only 13th worst, with about $860 million in flood damage adjusted for inflation, compared to the $4.5 billion in 2022-23 when a mild La Ni\u00f1a \u2014 the opposite of El Ni\u00f1o, with cooler-than-normal ocean waters \u2014 was present.<\/p>

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\u201cThe storms were spread out in 1997-98,\u201d Null said.<\/p>\n

There were 119 days in 1997-98 when it rained, nearly double the historical average. Had the storms been more closely packed together, flooding could have been calamitous, he said.<\/p>\n