An extraordinarily strong bout of seasonal king tides combined with runoff from the latest rainstorm on Friday to push the crest of the Petaluma River to its highest level in nearly three decades. As bay tides unleashed flooding in Marin County and other parts of the Bay Area, residents braced for a weekend of more rain and high winds.
The Petaluma River, one of Sonoma County’s largest tidal sloughs, had not breached its banks, but water levels surged to an impressive 8.33 feet by 1 p.m. Friday, according to a National Weather Service gauge at the D Street Bridge. The previous recorded high at this site was 6.4 feet, set in 1998. Meteorologist Rachel Kennedy of the National Weather Service said this new record could be broken again by late Saturday morning, as king tides were expected to peak in combination with an incoming rainstorm.
The National Weather Service issued a coastal flood warning for San Francisco Bay, in effect through Saturday afternoon.
“The king tides are the result of three different lunar events going on, which is why they are so strong,” Kennedy explained. These events include a full moon on Saturday night, perihelion—when the sun and moon align most closely and combine their gravitational effects—and perigee, when the moon is at its nearest point to Earth. In addition, Kennedy noted, a storm system is also bringing a 1.3-foot storm surge to the area.
“So that’s in combination with these king tides—they’re just unfortunately overlapping at the same time,” Kennedy said. The king tide is forecast to peak around 10:30 a.m. Saturday, potentially reaching 2.5 feet above average level—a height not recorded since 1988. Tide levels are anticipated to decrease by Sunday, but will remain elevated at about 1.9 feet above average along the San Francisco Bay shoreline.
Flooding on Friday prompted the California Highway Patrol to close parts of Highway 101 at Lucky Drive in Corte Madera and the Shoreline Highway in Mill Valley. In Tamalpais Valley, minor flooding was reported at Coyote Creek, which reached 8 feet Friday morning. Corte Madera resident Emily Drake took to her kayak to help stranded people along flooded streets and parking lots near Lucky Drive. She assisted a woman stuck at a flooded gym, ferrying her to a bus stop.
“I’ve been just going back and forth, talking to people and seeing if anybody knows anyone who needs to get to a dry spot,” Drake said. She expects the flooding to worsen Saturday morning, coinciding with the full moon. “I expect I’ll be doing a lot of rowing,” she added. “I’m hoping that it’s blocked off so not as many people need help.”
In Bodega Bay, king tides caused minor flooding of several shoreline parking lots. Petaluma officials, however, did not express concern about flood risk along the river, and no notifications or alerts were sent as of Friday afternoon. Most attention remained focused on Marin County, as Kennedy noted: “Typically Marin is our problem area for coastal flooding.”
Meteorologist Jan Null said this week’s tidal event will be in a class of its own. “This is going to be the maximum tide for the whole year,” Null said. “Everything is lining up at once. It’s not going to be end-of-the-world sorts of stuff. All of the lower-tier parking lots will probably be covered with water. Maybe some of the upper-tier ones, too.”
On Saturday, the highest tides are expected between 9:30 a.m. (near Pillar Point Harbor on the San Mateo County coast) and 10:30 a.m. farther north in Marin, with measurements between about five and seven feet, per the National Weather Service.
Beachgoers, beware: The combination of king tides and waves sent by stormy seas will make for hazardous coastline conditions over the weekend. Rain is expected to resume Friday night and last into Saturday, followed by a brief lull before showers return Sunday. Null said the rainiest areas—primarily the North Bay and Santa Cruz Mountains—could see as much as 4 inches of rain over a 96-hour period.
For updates, reach Petaluma Argus-Courier Editor Don Frances at [email protected].
Bay Area News Group contributed to this report.
https://www.pressdemocrat.com/2026/01/02/king-tides-and-winter-runoff-push-petaluma-river-to-highest-recorded-level-in-decades/
