With rumors of a hurricane in California, here’s what to expect

Forecasters are closely tracking the potential for Tropical Storm Marie to impact California’s weather over Labor Day weekend. Unusually warm waters in the eastern Pacific Ocean, where a potentially historic El Niño event is taking shape, are contributing to high levels of tropical cyclone activity this year. 

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Although models are showing a wide range of paths for Marie, the chances it would make landfall in Southern California remain extremely low. 

“No, a hurricane is almost certainly not going to make landfall in Southern California,” Daniel Swain, a climate scientist for University of California Agriculture and Natural Resources, said during an online briefing Monday. “[But] yes, it is increasingly plausible that a tropical system of some magnitude will have at least indirect effects in Southern California for several days later this week.”

Swain added that impacts like humid air, clouds and heavy surf were more likely than showers or thunderstorms. 

Forecasters from the National Weather Service office in Los Angeles agree. Depending on the track of the storm, there’s a very small chance of more than 2 inches of rain in Southern California; there’s a greater chance the state will stay totally dry, meteorologists reported on Tuesday. The most likely scenario is for some light to moderate rain to impact the holiday weekend. 

“The big question is where will it head after Saturday,” forecasters wrote about Marie. Some models show the storm moving north and right through Southern California by early next week. Others keep the storm turning to the west and missing California. “These are just two of many projections, but they do represent the two extreme scenarios between a major rain and wind event and little to nothing,” they explained. 

Meanwhile, there are two other tropical cyclones in the Pacific. Hurricanes Lowell and Karina might spin by Hawaii, but their impacts will most likely be much less than Hurricane Lala in August, according to Swain. 

Water temperatures are too cool in California waters to support a full-force hurricane, but occasionally storms get close enough to affect the weather and surf. The last time a tropical cyclone significantly impacted California was 2023. Hilary, a powerful hurricane that weakened significantly before making landfall in northern Mexico, brought record rainfall, flooding and mudslides to California. 2023-24 was also an El Niño year. 

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Only one intact cyclone has ever actually made landfall in California, a tropical storm — which is less strong than a hurricane — that hit near Long Beach in 1939. It was one of four cyclones that impacted the area during the El Niño of 1938-39. 

“If we had 10,000 years of data going back, we probably would see that a couple times a century, we get a significant tropical storm impact somewhere along the California coast — and then maybe once every century or so, we get an actual hurricane that manages to make it onshore,” Swain said. “But again, that’s assuming a climate that is cooler than the climate we have today. The oceans are warmer. There’s more hurricane fuel out there.”

Although there is unusual summer rain in the forecast for some parts of the San Francisco Bay Area this week, the cause is not the tropical activity. 

“It’s a relatively weak cold front that’s coming through,” Joe Merchant, a meteorologist with the weather service’s Bay Area office, told SFGATE. He added, “By late in the week, the front is well to the east, and then the updated track for that tropical system is expected to go more west than north at this point. Right now, the impacts are probably minimal from the tropical system.”

By the end of the week into the weekend, tropical activity will likely bring notable swells along the California coast, however. In Southern California, the National Weather Service is warning of high surf, minor coastal flooding and beach erosion around high tides.