Updated at 4:30 p.m. ET

No matter the adage or that the calendar tells us spring has sprung, March is still roaring like a lion on both sides of the country. On Wednesday, the West Coast braced for potential mudslides and flooding following heavy rain, and much of the East Coast dealt with a major snowstorm.

Southern California was on alert Wednesday as thousands of people evacuated their homes. Heavy rain combined with denuded land and loosened soil from recent wildfires made for a dangerous mix.

A flash flood watch was in effect for the region into Thursday, and forecasters called for several inches of rain from "a large and powerful storm system," with warnings that debris flow was likely.

Officials said a portion of State Route 33 in Ventura County was closed Wednesday because mud and debris flows.

In Los Angeles, the fire department was offering free sandbags and urging residents to remain alert. Officials called for evacuations beginning 6 p.m. local time for burn areas from recent fires.

Mudslides have already been a scourge in nearby Santa Barbara and Ventura counties, where the Thomas Fire was contained earlier this year. The state's largest wildfire on record burned for weeks, ravaging hillsides and leading to January's deadly mudslides.

On Tuesday, officials in Santa Barbara County issued a mandatory evacuation order for people in risk areas.

Rob Lewin, director of the Santa Barbara County Office of Emergency Management, said in a statement that the amount and intensity of the latest expected rain was enough to cause flooding, even without the recent fires.

"We could experience localized flooding and road closures which are not isolated to the burn areas," Lewin said. "The threat of rockfalls, mudslides and debris flow is high.

For some people, it is the sixth evacuation since December, reports The Los Angeles Times.

"I've gotten to the point where I just leave all my important documents in a zip-lock bag, ready to take at a moment's notice," Montecito resident Ashley Mayfield told the newspaper.

KPCC's Emily Guerin reports that many shops in Montecito were boarded up on Wednesday after the evacuation order. An exception was a Von's supermarket where store manager Aaron Berends said people were seeking the essentials: "Water, paper products and wine. This is Montecito."

Guerin reports that National Guard members were on standby with M1083 trucks to transport evacuees if needed.

ordered evacuations as well, opened shelters and closed schools.

On the other coast, from the Mid-Atlantic through the Boston area, a nor'easter Wednesday brought heavy, wet snow and wind and canceled flights, schools and work across the region.

The National Weather Service issued a winter storm warning into Thursday, saying significant snow, sleet and ice (some areas could see up to a foot-and-a-half) would make "travel very hazardous or impossible."

Parts of West Virginia and Kentucky were also expecting up to a foot of snow.

Thousands of flights were canceled or delayed Wednesday. New York's LaGuardia Airport said "nearly all" flight activity was suspended after noon on Wednesday.

Airports advised travelers to check on their flight status before heading to the airport.

Amtrak train service in the region was disrupted or canceled.

It was a snow day for students in Baltimore, Philadelphia, New York City and elsewhere as public schools closed for the day.

And some grown-ups got the day off too; federal offices in Washington, D.C. and Philadelphia's municipal offices were shuttered.

First lady Melania Trump tweeted an image of a truly white White House.

Brian O'Sullivan, 37, with the Fire Department of New York City, took advantage of the day to take his 3-year-old son, Rory, to a city park where they built a snowman.

"I have my little man with me, so that's the beauty of that job," O'Sullivan told WNYC.

Snow day fun aside, officials cautioned residents about risks associated with the weather.

New York City Mayor Bill de Blasio said wind gusts of up to 40 miles per hour could create dangerous blizzard-like conditions.

"If you don't need to be out this evening, don't go out," de Blasio said at a Wednesday afternoon press conference.

New York Gov. Andrew Cuomo declared a state of emergency Wednesday for several areas, including north of New York City, the city itself and Long Island. He also announced that 300 National Guard members would be deployed to areas impacted by the storm.

The nor'easter was the fourth major storm to hit the region in less than a month.

New Jersey Gov. Phil Murphy acted pre-emptively, declaring a state of emergency on Tuesday in order to ready emergency workers for "round-the-clock operations."

"We saw in the last couple of storms the biggest shortfall was the performance by the utilities," Murphy said at a press conference Tuesday. This time around, hundreds of utility workers were coming in from out of state to help, Murphy said.

Earlier this month, a storm known as a "bomb cyclone," owing to its rapid intensification, brought heavy winds to the East Coast, downing power lines and tree limbs, leaving around 2 million people without power and killing several people.

indicated several thousand power outages in Maryland, West Virginia and Delaware by midafternoon Wednesday.

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