No deaths or major injuries have been reported in Los Angeles from Tropical Storm Hilary, LA Mayor Karen Bass said at a news conference Monday.

While LA Fire Department Chief Kristin Crowley said no major damage has been confirmed, the mayor warned that "damage can occur in the hours and days after a storm hits, so Angelenos should continue to stay vigilant."

Mudslides and downed wires are also still a threat, Crowley cautioned, adding that residents should continue to avoid flooded roads.

She said rescuers on Sunday night responded to a flooded intersection where five cars were stranded. No one was hurt, she said.

The mayor added that no injuries were reported from Sunday's earthquake, which was unrelated to Hilary.

Rainfall totals from Hilary have reached 13.5 inches in San Bernardino County, California, and 11.7 inches in the mountains of Riverside County, California.

Los Angeles County recorded over 7 inches of rain while Palm Springs saw more than 3 inches, which broke the desert city's all-time daily summer rain record.

Bristlecone, Nevada, northwest of Las Vegas, recorded 8.4 inches of rain, including 6 inches in just 24 hours, breaking the rainfall record for a tropical cyclone or remnant in the state.

Hilary also brought fierce winds. In California, gusts reached a whopping 87 mph in the San Gabriel Mountains and 84 mph at Big Black Mountain.

-ABC News' Max Golembo

Flash flood warnings remained in effect on Monday in Los Angeles, Death Valley and some areas of southwest Nevada, after heavy rain fell overnight throughout the region.

Hilary weakened overnight into a post-tropical cyclone and was expected to dissipate in the high mountains of the Sierra Nevada.

Copious amounts of rain fell overnight, including the 10.5 inches that soaked Raywood Flat, California, a rocky area within the San Bernardino National Forest.

About 6.15 inches fell in Los Angeles. Palmdale, a city north of the Los Angeles, had its highest all-time daily rainfall with 3.57 inches.

Palm Springs got 2.82 inches, marking the city’s highest daily rainfall for summer and for August.

San Diego had 1.81 inches, its highest-ever daily August rainfall.

And Bristlecone, Nevada, near Las Vegas, picked up more than 6 inches, mostly within 24 hours. That rainfall broke the record for a tropical cyclone or remnant traveling through Nevada. It approached the 24-hour rain record for the state of 7.78 inches, which was set in 2004.

-ABC News’ Max Golembo

Thousands of customers in Southern California were without power at about midnight, with the highest number of outages in San Bernardino County.

About 14,000 customers were without power in that inland county, along with 7,600 in Riverside County to the south, according to PowerOutage.us, a site that tracks electric providers.

About 7,900 customers in Los Angeles County had experienced power outages as of about 6 p.m. on Sunday, the Los Angeles Department of Water and Power said.

"The City of Los Angeles is responding to reports of flooding, downed trees, and wires as well as other calls for service," the city's emergency officials said in an update. "Zero deaths have been reported in connection with the storm or earthquake thus far. At least 150 tree-related issues and eight mudflows have been reported."

By midnight, about 3,700 customers in Los Angeles were still without power, according to PowerOutages.us.

The National Weather Service has issued a flash flood warning for parts of Southern California as the region begins to experience the effects of Tropical Storm Hilary.

Los Angeles County, including downtown Los Angeles, and Ventura County were included in the advisory.

Heavy rain is now becoming more widespread across portions of the region. The heaviest rain is focused over much of the Interstate 5 corridor, north of San Diego into Los Angeles.

Rainfall rates up to 1 inch per hour are possible in this area, and flash flooding will likely develop, forecasts show.

Rounds of heavy rain are expected to continue to sweep across the greater Los Angeles metro area through the next several hours.

Hilary will then move northward over the next 24 hours. As the system moves over land, it will weaken and become disorganized but could remain a tropical storm as it tracks across Southern California.

A tropical storm warning remains in effect for San Diego, Palm Springs, Riverside and Los Angeles.

Flood watches remain across a large swath of the Southwest, including cities like San Diego, Palm Springs, and Las Vegas. These watches have also been extended northward up to Idaho for the potential for heavy rain and flash flooding early in the week.

The National Oceanic and Atmospheric Administration's Weather Prediction Center has issued a high risk alert for excessive rainfall across Southern, California, from Palm Springs to San Bernardino and up to Death Valley. "High Risk" days are rare and typically dangerous -- 39% of all flood-related fatalities and 83% of all flood-related damages in the U.S. occur on "High Risk" days, records show.

A moderate risk alert for extreme rainfall is in effect from Las Vegas to San Diego and Los Angeles.

The biggest rainfall totals will be across the mountains east of San Diego, north and east of Los Angeles. Through Monday, a widespread 1 to 3 inches of rain is forecast across much of Southern California, the desert Southwest and across southern Nevada.

Three to 6 inches or more of rain is forecast across the mountains areas in Southern California. Several inches could still fall in some desert locations, with the greatest chance closer to Death Valley. Isolated amounts of 6 to 10 inches are still possible in some regions.

One to 2 inches of rainfall quickly falling in a desert location can cause major impacts due to the oversaturated soil.

-ABC News' Daniel Peck