Governors whose states lie in the path of Hurricane Sandy on Monday urged skeptical residents to heed their dire warnings and prepare for one of the worst storms to hit the northeastern US in years.

From Connecticut through New Jersey and down into Maryland, they cautioned that the storm would likely result in fatalities, devastating floods and tidal surges, and power outages that could last for days.

"Hurricane Sandy is going to come over Maryland, she's going to sit on top of Maryland and beat down on Maryland for a good 24 to 36 hours," Governor Martin O'Malley said.

"This is going to be a long haul," he told reporters at the state's emergency coordination center. "The days ahead are going to be difficult. There will be people who die and are killed in this storm."

Cutting an exceptionally wide swathe, Sandy was expected to make landfall later Monday in a populous section of the Mid-Atlantic coast where New Jersey, Delaware and Maryland converge.

"Don't be fooled. Don't look out the window and say, 'It doesn't look so bad'," said New York Governor Andrew Cuomo, quoted by US news media. "The worst is still coming."

"There's going to be a long period of time for some folks where we're going to be without power here," his New Jersey counterpart Chris Christie told CNN. "We are only at the beginning of the storm."

"We anticipate that if current predictions hold that this will be the largest and perhaps most serious event" ever faced in Connecticut, its governor Dan Malloy told CNN, citing the threat of tidal surges in Long Island Sound.

Like other governors, Malloy worked his Twitter account hard, sending out missives like: "Please stay indoors. You are risking your life going outdoors to experience the storm. Winds are too strong right now, it's not worth it."

"The most important first responders are the moms and dads who will keep their families safe," tweeted O'Malley.

The small state of Delaware, squarely in Sandy's path, banned driving altogether Monday except for emergency vehicles, under a law that could see repeat offenders sent to jail.

"We didn't want people driving to work and then driving back in dangerous conditions or getting stuck," said Delaware Governor Jack Markell.

In Virginia, Governor Bob McDonnell encouraged citizens Monday "to check in on neighbors, friends and family, particularly the elderly, as this storm unfolds. We need to look out for each other."

Dire warnings also came from inland West Virginia, where moisture from Hurricane Sandy colliding with an incoming cold front prompted blizzard warnings in at least 14 counties in the Appalachian state.

"We cannot be certain of the impact this storm will have on our state," Governor Earl Ray Tomblin said, who declared a state of emergency Monday. "For this reason, we are preparing for all scenarios."

Maryland's O'Malley said that while the potential for loss of life was his "biggest concern right now," Hurricane Sandy's slow approach gave state officials several days of valuable time to prepare for its wrath.

Twenty-three emergency shelters have opened around Maryland for those most in need, he said, but most citizens should "hunker down" and remain indoors with their families until the "monster storm" passes.

"There will undoubtedly be some deaths that are caused by the intensity of the storm, by the floods, by the tidal surge, and by the waves. The more responsibly citizens act, the fewer people will die."