Harry and Meghan’s star-studded neighbourhood of Montecito was ordered to evacuate as a fatal storm closed in on Tuesday morning.
The stark warning came as a boy, 5, was washed away by rushing flood water with rescuers only recovering his shoe.
The boy’s mother was driving a truck when it became stranded in floodwaters near Paso Robles, a small city inland from California’s central coast.
Bystanders were able to pull the mother out of the truck, but the boy was swept out of the vehicle and downstream.
A seven-hour search for the missing boy turned up only his shoe before officials called it off as water levels were too dangerous for divers.
The death toll from the storm system hit 14 on Monday, after two people killed by falling trees.
Thousands have been left without power and in Los Angeles, a sinkhole swallowed up two cars with two passengers rescued by an aerial ladder and suffering just minor injuries.
Montecito, which was hit by deadly mudslides just five years ago, is squeezed between mountains and the Pacific and is home to celebrities including Rob Lowe and Harry and Meghan, the Duke and Duchess of Sussex.
The town of about 9,000 people, a favourite of American entertainment royalty such as Oprah Winfrey and Jennifer Aniston, was expected to get up to eight inches of rain in 24 hours - on hillsides already sodden by weeks of downpours.
Ellen DeGeneres urged residents of the exclusive enclave to “stay safe” as the area continues to experience “unprecedented” weather conditions.
The US talk show host and comedian posted a video of herself from near her home, which she shares with spouse Portia de Rossi, beside a rushing river.
Speaking in a video on her social media accounts, DeGeneres said: “This is crazy”.
“We are having unprecedented rain. This creek near to our house never flows ever (and it’s) probably about nine feet up.
Montecito is under mandatory evacuation. We are on higher ground so they asked us to shelter in place. Please stay safe everyone. pic.twitter.com/7dv5wfNSzG
— Ellen DeGeneres (@EllenDeGeneres) January 9, 2023
“It could go another two feet up. We have horses ready to evacuate.”
“We need to be nicer to Mother Nature, because Mother Nature is not happy with us.”
DeGeneres added in the caption of her post: “We are on higher ground so they asked us to shelter in place. Please stay safe everyone.”
Tens of thousands of people remained without power, and some schools closed for the day, with streets and highways flooded and trees felled.
Santa Barbara County Sheriff Bill Brown said the decision to evacuate nearly 10,000 people was “based on the continuing high rate of rainfall with no indication that that is going to change before nightfall”.
