ATLANTIC CITY, N.J. — Hurricane Sandy strengthened slightly on its way to a predicted direct hit on New Jersey, with tidal waters crossing the main oceanfront drive in the south end of Cape May early Monday in the first sign of what is to come.

The storm was still hundreds of miles away, but heavy rain and strong winds began pelting southern New Jersey. Large, frothy waves pounded the coastline, and officials braced for a storm surge that was expected to cause flooding.

Thousands of people fled to what they hoped would be safer ground. Towns across the state issued voluntary evacuation orders; some made them mandatory.

The streets of Atlantic City were mainly deserted.

Tom Foley, Atlantic City's director of emergency management, said officials were sweeping the city's low-lying areas, looking for people who were still in their homes. Two shelters are currently occupied, he said.

"We're anticipating more people coming in as the tide rises," he said.

More than 2,300 homes and businesses were without electricity early Monday, mainly in Monmouth and Cumberland counties. That was down from more than 5,000 earlier.

President Barack Obama signed an emergency declaration for New Jersey on Sunday, allowing the state to request federal funding and other assistance for action taken in advance of the storm.

Christie, who famously urged New Jersey residents last year to "get the hell off the beach" as Hurricane Irene approached, urged residents of the state's narrow barrier islands to move to higher ground. He predicted the storm would come ashore at Atlantic City around 2 a.m. Tuesday.

"Don't be stupid. Get out," he warned.

More than half of New Jersey's 590 school districts decided to close for Monday, and 247 districts have decided to remain shut Tuesday, as well.

Sandy was just one component of a massive storm predicted to come together over the eastern third of the U.S., threatening damaging wind, possible record-setting flooding and prolonged power outages. At 5 a.m. Monday, the National Hurricane Center indicated that Sandy had strengthened a bit since last check, with top sustained winds of 85 mph.

"I think this one's going to do us in," said Marc Palazzolo, owner of a bait and tackle shop on an inlet to the ocean in Point Pleasant Beach. He used the same wood he boarded up the store with in past storms to secure it this time, crossing out the names of hurricanes Isaac and Irene and spray-painting "Sandy" next to them.

"I got a call from a friend of mine from Florida last night who said, 'Marc: Get out! If it's not the storm, it'll be the aftermath. People are going to be fighting in the streets over gasoline and food," he said.

Yet Palazzolo was floored by the response to a Facebook plea he issued Saturday night for people to come help him fill sandbags to protect his shop and nearby buildings. Thirty people showed up, many of them strangers. One man drove more than two hours from Bergen County to pitch in.

Christie said a southern-state landfall will cause more flooding in the Raritan River area, while a Monmouth County landfall will result in more extensive inland flooding of the Passaic River.

Atlantic City's 12 casinos closed for only the fourth time in the 34-year history of legalized gambling here. State parks also shut down.

Residents of northern New Jersey river communities braced for another round of the flooding that has become commonplace for them. Pompton Lakes has been hit by flooding several times in the last decade, most notably last year after the remnants of Hurricane Irene swept through the area and left dozens of businesses and homes severely damaged.

Some in the town were already putting belongings out near the curb, in advance of the storm.

"People are worst-case-scenario-ing it," said Kevin Gogots, who has lived in the town since the early '80s. "They're figuring, divide and conquer: They'll take the stuff they want to save and put the rest out. Of course, if the street floods again we'll just have things floating around."

Associated Press writer David Porter in Pompton Lakes contributed to this report.