For a month, the 2026 El Niño's Kelvin wave has been reported as something on its way. The tide gauges show it has already arrived. On October 1, water at San Diego ran 1.21 feet above the predicted tide and Los Angeles ran 1.08 feet above it. San Francisco ran 0.79 feet above, and Port Chicago, on Suisun Bay at the mouth of the Delta, ran 0.75 feet above. All four readings were still rising.

Measured against the average of the last three Septembers, the gauges are about 11 inches high in Southern California and 6 to 7 inches high in the Bay and Suisun Bay. The signal has reached the San Joaquin River at Stockton, where the September average stage ran about 3 inches above the previous three Septembers. The September and October 2026 tide readings are NOAA preliminary data. NOAA has not yet completed its quality review, and the figures may shift slightly once it does.

The wave will not flood Lodi. What it does is raise the starting water level for every tide and storm this winter, across the Bay and into the Delta channels that drain the Mokelumne. The winter's highest tides arrive November 24–26 and December 23–25. Researchers expect two to four more Kelvin waves before spring.

California entered fall under a statewide emergency proclamation and a forecast for one of the strongest El Niño events on record (NOAA outlook). That is not a prediction that Lodi will flood. The local preparedness questions center on storm drains in town, the Mokelumne River corridor through Woodbridge and Thornton, north-Delta levees, and access to the White Slough wastewater plant west of Interstate 5.

Governor Gavin Newsom proclaimed the emergency on September 21. The proclamation itself warns that “very strong El Niño events do not produce uniform statewide outcomes.” This report sets out what each flood scenario would look like around Lodi, which parts can be mapped from official data, which cannot, and what local agencies can finish before the storms arrive.

Northern California has been impacted by a series of powerful atmospheric river storms that began in late December 2025 and continued through the first week of January 2026. As of January 6, 2026, the most intense rainfall has passed, but residual flooding effects persist across the Sacramento Valley region.

Northern California is under a prolonged, high-impact atmospheric river pattern bringing several days of heavy rain, and flooding concerns from the Sacramento Valley through the northern San Joaquin Valley. Sacramento, Elk Grove, Lodi, and Stockton are all under flood watches, through at least December 26