Severe storms are expected along the coast of Northern California, and evacuation orders and warnings have been issued in some areas.
Areas that have been hit by wildfires in the past are among the first to be evacuated due to the threat of flooding and landslides.
California’s governor has declared a state of emergency for the second flood in a week.
Meteorologists say it could turn into a bomb cyclone (a type of explosive storm) and kill people.
Northern California is expected to be the hardest hit after a levee breach over the weekend.
The National Weather Service (NWS) has issued a flood and gale warning for the entire Northern California Bay Area, saying gusts of wind are expected to knock down trees and power outages.
It warns that the North Fork Dam is in critical condition and that the spillway will overflow on Thursday morning. The NWS is calling on people in low-lying areas under the dam to “move to higher ground immediately.”
“Simply put, it’s going to be one of the most far-reaching systems this meteorologist has seen in a long time,” said a forecaster in the region. .
“Flooding, washed out roads, collapsing hillsides, fallen trees (even whole groves), widespread power outages, immediate stoppage of commercial activity and, most importantly, loss of life are expected,” it said.
“This is a really cruel system and we have to take it seriously.
It is expected to become a “bomb cyclone”, a type of storm that intensifies rapidly, which is common on the east coast of the United States and Canada.
Santa Cruz County, south of San Francisco, has been ordered to evacuate due to a “high probability” of flooding causing areas to become inaccessible.
Further south, in Santa Barbara County, authorities have ordered residents living near the remains of past wildfires to leave the area.
The order affects the wealthy community of Montecito, home to the Duke and Duchess of Sussex, Harry and Meghan, and Oprah Winfrey.
School districts in Northern California canceled Thursday’s classes, including 8,000 students enrolled in public schools in San Francisco.