SAN FRANCISCO — Residents of Northern California hunkered down Sunday as a powerful storm drenched the area with yet another round of pounding rain and strong winds.
The latest storm system — the third to hit the area in less than a week — moved across the region Saturday and Sunday, dropping as much as an inch of rain per hour in some areas, toppling trees, and knocking out electrical service to tens of thousands of people, officials said.
With rivers across Northern California swelling from the deluge, the National Weather Service warned that several rivers were in danger of topping their banks late Sunday or early Monday.
Flood warnings were in effect for the Napa and Russian rivers, two rivers north of San Francisco with a history of flooding, as well as the Truckee River, near Lake Tahoe.
‘‘We’ve been in preparation mode since Thursday,’’ said Barry Martin, a spokesman for the city of Napa. In bracing for the storm, city officials had handed out more than 8,000 sandbags and about 150 tons of sand, Martin said.
The Napa River hit flood stage Sunday, though most of the flooding was expected to be in agricultural areas outside of the city of Napa, officials said. In Sonoma County, the Russian River was expected to top its banks Monday morning, forecasters said.
Elsewhere, officials were preparing for flooding near Truckee, Calif., a small town of about 16,000, as the Truckee River neared the top of its banks. But weather officials were heartened by the speed in which the system moved through the area, meaning rainfall amounts could be less than predicted. And with colder temperatures than expected in the mountains, more snow and less rain was falling.
‘‘I’m not sure by how much it could lower the flood threat yet,’’ said Gary Barbato, a NWS hydrologist said early Sunday. ‘‘Maybe dramatically but we’ll have to see,’’ he said.