"We should not underestimate this storm," New Jersey's Gov. Christie said Saturday in North Wildwood.
Coastal residents were instructed to relocate to higher ground, and inland residents were told to prepare for up to a week without power.
The rain in Philadelphia is forecast to become steady by Sunday evening, with winds above 30 m.p.h. early Monday. By midnight Monday, gusts in Philadelphia could exceed 60 m.p.h., according to the National Weather Service.
The region's electrical utilities, stung by criticism they were unprepared for the damage caused by last year's twin storms of Irene and Lee, put out a nationwide 911 call for help from other power companies. Convoys of bucket trucks from Kansas, New Orleans, Chicago, and Florida hit the road for the East Coast.
"People should be ready for the possibility of power outages paired with cold temperatures," said Craig Fugate, administrator of the Federal Emergency Management Agency. "Now is the time to prepare. Review your emergency plans, check your supplies, and stay informed."
The storm could be more fearsome than Irene, which caused more than $15 billion in damage. Forecasters said hurricane-force winds of 75 m.p.h. might be felt 100 miles from the storm's center.
Sandy was briefly downgraded to a tropical storm Saturday morning. But Marshall Moss, vice president of forecasting at AccuWeather Inc., said it hardly matters what you call it; the storm will wreak havoc for hundreds of miles.
"It's going to affect millions and cost billions," he said. The storm will cause flooding and power outages that could last for days or weeks.
The storm is an unusual combination of a tropical weather system with a cold air mass that Moss called a "truly historic" event and said would act more like a nor'easter than a hurricane.
Most jurisdictions in the area - New Jersey, Pennsylvania, Philadelphia - declared states of emergency and set up shelters in anticipation of the storm.
New Jersey ordered evacuation of most of its barrier islands, including Atlantic City, by 4 p.m. Sunday.
"They're going to close down the bridges," said Mary Goepfert, a spokeswoman for the New Jersey Office of Emergency Management. "You can't have people driving on an elevated bridge in 70 m.p.h. winds."
She said people who do not evacuate will find it "extraordinarily difficult to get help."
Officials planned to waive outbound tolls on the Garden State Parkway and the Atlantic City Expressway starting at 6 a.m. Sunday to facilitate the coastal evacuation.
Christie said he did not like telling people to leave their homes but had no choice. He said the barrier islands would be lashed by hurricane-force winds for 24 hours or more. "It is simply unsafe for people to be there," he said.
Christie's office issued a warning to merchants who jack up prices during the storm. "Price gouging is illegal," the administration said, and violators will face "significant penalties."
Public officials attempted to overcome complacency.
Philadelphia officials encouraged residents of flood-prone areas to evacuate, and Mayor Nutter said emergency shelters would open at 4 p.m. Sunday at West Philadelphia High School, Roxborough High, and Samuel S. Fels High School.
The shelters will have food, water, and safe sleeping areas, and medical care will be available. Nutter said pets would be welcome at all three shelters. Officials will decide Sunday whether Philadelphia schools will open Monday. The three high schools could host evacuees and remain open as school buildings, said Fernando Gallard, a spokesman for the school district.
Nutter said he thinks people will get the message and go to higher ground. "Philadelphians are smart enough to figure out 'This is real, this is serious, we'll do what we've got to do.' "
Many residents said they were unworried.
"Last year's hurricane didn't get as close to us as we thought, so we currently have no preparations planned," said Steve DeLong, general manager of the Bourbon Blue restaurant on Main Street in Manayunk.
DeLong complained that news media had exaggerated storm threats to Manayunk in the past, harming business.
"We're going to be open," he said. "The only way we'll close is if the power's out."
In Miquon, the Montgomery County community where some residents live only a few feet above the Schuylkill, residents said they had no plans to evacuate.
"I didn't go out and stock up," said Julia Dechristoforo, 34, who has lived along the river for nine years. "We're used to it."
Public-works employees have scrambled in recent days to clear storm drains, and transit agencies were making plans to reroute flooded bus lines. Amtrak canceled some service for Sunday along the Eastern Seaboard and urged travelers to get out early in the day.
SEPTA expects to keep its Market-Frankford and Broad Street subways running, spokeswoman Jerri Williams said.
Philadelphia International Airport said it was preparing for potential disruptions, and some airlines are letting travelers change their plans without having to pay penalties.
Hectic at groceries
Refinery operators announced no plans to shut production.
Grocers said shoppers were taking the warnings to heart.
"They're hectic, to say the least," said Lou De Francesco, manager of McCaffrey's Market in Yardley. His supply of D batteries was exhausted.
Todd Allen, who manages the Wegmans in Mount Laurel, said he was surprised that many shoppers were buying perishable food, considering the risk of power outages.
Allen said that sales were easily double or triple the norm but that Monday and Tuesday likely would be slow. The store has arranged for 15 to 20 employees to sleep in an office to keep the store open in an emergency.
New Jersey officials warned utilities to improve their storm response over last year, and Christie encouraged the Legislature to pass a law to raise penalties on utilities for failure to restore service promptly. The current penalty is $100 a day; Christie favors a fine of $25,000 a day, capped at $2 million.
"I think that will get their attention," he said.
Pennsylvania utilities also were criticized for an inadequate response to Hurricane Irene in 2011, which knocked out more than 1.3 million Pennsylvania customers. Some customers remained without power for up to 10 days.
The utilities experienced breakdowns in communications with customers. Call centers were overwhelmed, and automated systems dropped numerous callers.
Peco Energy Co., which won industry plaudits for restoring service within 72 hours to nearly all of its 511,000 customers who lost power last year, said Hurricane Sandy was comparable to Irene.
Karen Muldoon Geus, a Peco spokeswoman, said the utility had 300 line crews and 150 tree crews on standby. Utilities from Chicago, Tennessee, Kentucky, Mississippi, and Louisiana are also dispatching crews to assist.
Peco has positioned trailers near flood-prone areas to act as operations centers during restoration activities, she said.
"We expect if we get a direct hit, the storm will result in a multiday restoration effort," she said.
For the latest on Hurricane Sandy, including more photos and video, visit www.philly.com.
Contact Andrew Maykuth
at 215-854-2947, @Maykuth on Twitter, or email@example.com.
Inquirer staff writers Joseph A. Gambardello, Kristen A. Graham, Jonathan Lai, Linda Loyd, Paul Nussbaum, Amy S. Rosenberg, Joe Trinacria, Jackie Urgo, Aubrey Whelan, and Anthony R. Wood contributed to this article.