Nearly the entire population of California is under flood alerts as rain drenches the state

(CNN) — There’s a significant flood threat in Los Angeles and nearly the entire population of California is under flood alerts as rain drenches the already-soaked state. Officials are urging people to stay off roads as they face the risk of flooding and landslides.

• Torrential rainfall triggers flash flood warnings: Flash flood warnings were issued Monday morning for Santa Barbara and Ventura counties, where 3 to 6 inches of rain deluged the coast and up to 8 inches fell in the nearby foothills. An additional flash flood warning was issued for part of Los Angeles County a few hours later.

• Around 37 million people under flood alerts: Rounds of rain are soaking large portions of California Monday, but the heaviest is targeting Southern California. Heavy rain shifted away from Santa Barbara and Ventura counties Monday morning and into the greater Los Angeles area by the early afternoon.

• Airport and roads closed by flooding: The Santa Barbara Airport was closed due to flooding on Monday morning, the airport announced on X. There were “numerous reports of flooding and rock and debris across roads,” the National Weather Service in Los Angeles said. Several roads across the state were closed because of flooding and rockslides, California’s transportation agency reported.

• Water rescues: Two people were safely removed from a flooded vehicle in San Luis Obispo County Monday morning, according to fire officials. A photo from the scene showed a vehicle submerged to the hood in muddy-brown floodwaters.

• Rare severe weather risk: A Level 2 of 5 risk for severe thunderstorms is in place for California’s Sacramento Valley Monday – the first such forecast since February 2015. Severe thunderstorms packing damaging wind gusts, hail and even a couple of brief tornadoes may develop Monday afternoon and evening.

• Evacuation warnings issued: Officials in Santa Barbara County issued evacuation warnings for several flood-prone areas Saturday in advance of the storm. An evacuation warning was issued Monday for a portion of southwestern Los Angeles County over mud and debris flow fears, according to the sheriff’s office.

Days of rain to keep flood threat elevated

Heavy rain will continue beyond Monday as the atmospheric-river-fueled storm stalls just off the West Coast. The Weather Prediction Center has issued excessive rain outlooks through Tuesday for much of California.

Rain will persist across a large portion of the state Tuesday, but torrential deluges will become more isolated in nature as the storm’s atmospheric river connection weakens.

Even so, the drenched ground will have little ability to tolerate any additional rainfall and flooding remains a considerable concern.

Major cities facing the most flood risk over the next couple of days include Los Angeles with a Level 3 of 4 risk on Monday and Tuesday, and Santa Barbara with a Level 2 of 4 risk on Monday and Tuesday. San Diego is under a Level 2 of 4 risk on Tuesday.

The Los Angeles office of the National Weather Service warned “significant flooding” is possible and 2 to 5 inches of rain are expected – with up to 10 inches in isolated areas of the Santa Lucias and Santa Ynez ranges.

Downtown Los Angeles could pick up between 2 and 3 inches of rainfall from Monday afternoon through Tuesday. Add this to the historic rainfall the city recorded earlier in the month, and this February could become Los Angeles’ wettest on record.

Both this week’s storm and the prolific early February storm were fueled by atmospheric rivers. However, the ongoing storm is tapping into much less moisture than the early-month storm and therefore is unlikely to become as extreme.

Warnings of possible large mud or rock slides on canyon roads and debris flows in areas recently burned by wildfires were also issued by the forecast office in Los Angeles.

An early round of rain arrived Friday night and Saturday with a separate storm. The early-weekend rain soaked soils in Northern California’s Del Norte County and caused a rock slide that shut down a portion of U.S. Highway 101.

The city of San Francisco, which also is under a Level 2 flooding rain risk through Tuesday, is providing some residents and businesses with 10 free sandbags. Officials are concerned about “excessive runoff from moderate to heavy rain,” which may lead to flooding, according to a post from the city on X.

Portions of the Bay Area picked up 0.75 to 1.5 inches of rain from Friday night to Monday morning, with higher amounts of 2 to 3.5 inches in the higher terrain near the coast.

Flooding began north of the Bay Area Sunday night. Sonoma County fire officials captured video of riverlike floodwaters running across a fully-submerged road.

Rounds of rain will finally come to an end in California by late Wednesday as the main storm driving the soaking weather pushes eastward, crossing into the Rockies.