NEW YORK - Airlines canceled 300 flights Sunday as a hard-blowing nor'easter gathered strength along the East Coast and threatened to deliver some of the worst flooding to coastal Long Island in 14 years.

The cancellations at the New York area's three major airports affected most carriers, said Steve Coleman, a spokesman for the Port Authority of New York and New Jersey. More cancellations were expected throughout the day.

Forecasters expected sustained wind of 40 mph and a storm surge of 3 to 5 feet, a combination that could cause as much coastal damage as a winter storm that wreaked havoc on the island in late 1992, Gov. Eliot Spitzer said.

Heavy rain and thunderstorms extended from Florida up the coast to southern New England on Sunday morning.

Spitzer said some low-lying areas of Long Island may need to be evacuated, and he deployed 3,200 members of the National Guard to potential flood areas.

The weather system was forecast to strengthen along the East Coast and form a nor'easter, a storm that follows the coast northward with northeasterly wind driving waves and heavy rain.

The National Weather Service posted storm warnings and watches all along the East Coast, with tornado warnings in South Carolina and flood warnings extending from Virginia north to the New York area. Winter storm warnings were in effect for parts of New England.

Two to 4 inches of rain was forecast for the New York City region with wind gusting to 50 mph. Snow and sleet were possible inland, the weather service said.

The weather service said as much as 20 inches of snow was possible at higher elevations of New York's Adirondacks by the time the storm passes late Monday and Tuesday.

Pennsylvania officials activated the state emergency operations center in anticipation of the storm. "While snowfall in April is highly unusual, it is critical to remain vigilant in executing winter weather preparedness plans," Gov. Ed Rendell said in a statement.

New Jersey made preparations for heavy snow in the state's northwest corner and possible flooding elsewhere. "We're ready for everything, which based upon the forecast, is pretty much what we could get," said Joe Orlando, a spokesman for the state Department of Transportation and the New Jersey Turnpike Authority.

The storm also rained out Sunday's Washington Nationals game with the New York Mets at New York's Shea Stadium. Last weekend, snow dumped by another major storm system wiped out scheduled Mariners-Indians games at Cleveland for four straight days.

Organizers canceled the Greek-American Independence Day parade that had been planned on Fifth Avenue.

"It is unusual for this time of year. We probably see a storm like this, at this time of year, probably once every 25 years or so," said Brian Korty, a meteorologist with the National Weather Service in Camp Springs, Md.

The storm had been blamed for five deaths as it blew out of the Plains late in the week, two in violent thunderstorms in Texas and three on slippery roads in Kansas, where more than a foot of snow fell. Two tornadoes caused damage Friday in Texas.