By Ralph Ellis and Eliott C. McLaughlin

CNN

(CNN) -- The winter storm that socked the Southeast has moved up the East Coast, promising heavy snow and frigid temperatures early this week for millions of people in the Northeast.

As of late Saturday, Boston had seen a half foot of snow, but the southeast portion of Massachusetts was hit harder, particularly the Cape Cod area. Hanover recorded 17 inches of snow, Middlesboro 16 and East Bridgewater 15.

Parts of New Jersey, New York, Delaware, Maryland, Rhode Island, Virginia and North Carolina saw 10 inches or more as well.

The town of Barnstable, on the Cape, said 1-3 inches of snow could fall per hour and urged residents not to park on the main street because of snowplows.

Going back to work Monday could be treacherous. Temperatures won't rise above freezing until Tuesday, the National Weather Service said.

As the snow has moved out of the Eastern United States, cold temperatures have rushed in, and residents all along the Eastern Seaboard can expect Sunday highs to be 10 to 20 degrees below normal highs.

Boston Mayor Marty Walsh urged the city's citizens to look out for each other and help keep the streets cleared.

"If we can all work together to remove the snow rather than push it around, we'll be in good shape for Monday morning," he told CNN affiliate WBZ.

Travel problems

Thousands of travelers had flights canceled up and down the East Coast because of the winter weather and the shooting at Fort Lauderdale-Hollywood International Airport in Florida.

Alexia Marramarco, a French foreign exchange student on her way back to Georgia State University in Atlanta, was one of them.

First, her flight Friday from Paris to Fort Lauderdale was diverted to Miami because of the shooting. Then, after being bused to Fort Lauderdale, Marramarco learned her connecting flight to Atlanta was canceled because of weather.

"I haven't slept," she said Saturday.

Asked if she thought she'd get back to campus by Saturday night, she said, "Je ne sais pas." ("I don't know.")

The Fort Lauderdale airport closed one of its four terminals after the shooting but reopened it for flights on Saturday afternoon.

FlightAware, an airline tracking website, listed more than 2,100 cancellations within, into or out of the United States by 6 p.m. ET Saturday. Airports in Boston and Philadelphia urged travelers to check with their carriers about their flight status. The number dropped to fewer than 1,800 by Sunday afternoon.

Drivers also ran into problems.

A pileup involving as many as 20 vehicles shut down a section of Interstate 91 near Middletown, Connecticut, on Saturday afternoon, WBZ reported. No serious injuries were reported.

In Virginia, one highway fatality occurred Saturday afternoon when an SUV ran off a road in Greene County, the Virginia State Police said. State police responded to 527 traffic crashes on Saturday.

North Carolina State Highway Patrol troopers have responded to nearly 1,500 calls for service and more than 700 vehicle collisions since midnight.

North Carolina

North Carolina took a heavy punch Friday night, with CNN affiliate WRAL reporting that Raleigh saw about 2 inches of snow but surrounding areas, including Orange and Durham counties, got 6 inches or more.

Though snow tapered off Saturday, driving conditions will remain hazardous because of low temperatures and ice on the highways.

"Throughout Monday the weather is going to be pretty cold and whatever is on the road will still be there," Gov. Roy Cooper said. He said that, so far, there are no weather-related fatalities.

Cooper said 9,300 customers were without power Saturday afternoon, down from 25,000 earlier in the day. Fewer than 3,000 remained without power Sunday afternoon, according to Duke Energy.

The weather was so bad in the Triangle area that the Saturday night basketball game between the University of North Carolina and North Carolina State University was postponed until 1 p.m. Sunday.

Georgia

The storm that Atlantans were warned about Friday, sending them flocking to the grocery store, didn't pan out for the most part.

Three to 5 inches of snow were predicted, but only a dusting of snow fell on the city, though icy conditions persisted through Sunday and conditions stayed below freezing. Wind chill was also a problem.

A motorist was killed Saturday when his car struck a patch of ice on a bridge and he lost control of his vehicle. Authorities said inclement weather and excessive speed contributed to the accident.

The storm had knocked out power to more than 10,000 customers across metro Atlanta by early Saturday, Georgia Power said. All but a few hundred homes and businesses saw their power restored by Sunday afternoon.

Florida

It didn't snow in the Sunshine State, but storms forced the cancellation of the Walt Disney World Half Marathon. This was the 20th anniversary of the event, which was sold out.

There was a tornado watch for western Florida, around Tampa. Event organizers in Orlando delayed and then canceled the race because of strong winds and lightning in the area.

The West

Four people died in California over the weekend as a series of storms pounded the state.

One person died and another was hospitalized after being trapped in a car in the water Sunday morning near the Oakland International Airport, CNN affiliate KRON reported, citing fire officials.

Two people died in solo spinout accidents most likely due to the heavy rain in the San Francisco Bay area, California Highway Patrol Officer Custodio Lopez said.

"Both of these accidents are still under investigation so we don't know for certain it's from the rain, but they both occurred on wet roadways and were solo spinouts so we believe weather was a factor," Lopez said.

One accident happened Saturday morning in the Oakland area and the other occurred Saturday night in the Hayward area, Lopez said.

A woman was killed Saturday morning after a tree fell on her at the Canyon Lakes Golf Course in San Ramon, authorities there said.

Flooding is likely in the coming days, forecasters said.

While moderate to heavy storms were predicted to persist through Monday, producing snow in the higher elevations and rising water levels elsewhere, a second storm will pass through the West Coast on Tuesday and Wednesday.

The rain is expected to melt the snow at the higher elevations, which threatens to overload dams and reservoirs in California. All the gates at the Nimbus Dam near Folsom, California, have been opened to let the water flow downstream.

Along with heavy rain, the National Weather Service forecast mountain snow in the West over the weekend, with flooding likely across central and Northern California, western Nevada and coastal Oregon.

Nevada Gov. Brian Sandoval has "declared a state of emergency due to the severe weather system developing in north Nevada and the possible danger to life and property."

Overall, 24 million people are under a winter weather advisory or warning across the Southeastern United States and in the Northwest, including the Sierras in Northern California.

CNN's Haley Brink, Judson Jones, Azadeh Ansari, Brandon Miller, Phil Gast, Brandon Griggs, Joe Sutton and Dave Alsup contributed to this report.