An atmospheric river will continue to bring heavy rain, urban and river flooding, and strong winds to the Bay Area through Tuesday. There is also an increasing chance for thunderstorms in the afternoon, according to the National Weather Service.
“The Bay Area is now in the cross-hairs of the atmospheric river,” the forecast states.
While less impactful in the second half of the week, rain could continue through Friday.
Richmond, which has seen 4.5 inches of rain in the past seven days (the highest total in Contra Costa County aside from the Mount Diablo peak) could receive up to 2.5 inches. It’s among areas under a flood advisory until 4 a.m. Wednesday. There is also a wind advisory until 11 p.m. Tuesday, with some parts of the Bay Area under a gale warning, with winds of 30 to 30 mph and gusts up to 60 mph expected.
The rain comes as somewhat of a relief for the Bay Area after a historically drier water year, a hydrological timeframe starting in October instead in January. Water year 2025 continues to have above average accumulated precipitation when considering the state’s average, according to the California Department of Water Resources, which reported that as of the end of December, when the statewide accumulated precipitation through the end of December 2024 was 9.4
inches, which is 115% of average.
This season Richmond has had 14.7 inches or rain, according to Contra Costa County Flood Control. (Click the datasets tab at the top left of the map below to view local rainfall totals for various time periods.)
‘Moisture conveyor belts’
National Weather Service meteorologist Dalton Behringer said that an “atmospheric river,” might remind Californians of the back-to-back storms between 2022 and 2023 that brought flooding to much of the state. While the term is scientific, he added, it is not one that the Bay Area’s NWS office uses lightly, lest it conjure fears of a biblical downpour.
When California does have significant rain events, they are often due to atmospheric rivers, simply because of the state’s position on the continent. Atmospheric rivers are categorized as long, narrow atmospheric regions that carry water vapor from the subtropics. The moisture for the storm expected to come today is sourced from this region, thus making it a traditional atmospheric river.
Despite the apocalyptic name, Behringer emphasized that atmospheric rivers are regular phenomena that only really cause issues when they linger too long. (The term has been around for decades, and it’s still the subject of scientific dispute. Some researchers prefer the more workaday name of “moisture conveyor belt.”).
“People start freaking out and thinking that it’s going to be this big, flooding rainfall event,” he said, “when really that only happens when they stall over a certain area.”
Richmondside Editor-in-Chief Kari Hulac contributed to this report.
