Tens of thousands New Hampshire residents lost power early this afternoon as Hurricane Sandy started its slow, determined assault on must of the eastern United States.

Public Service of New Hampshire reported that 17,800 of its customers were without power, about 3 percent of its total customer base. Several thousand lacked power in Dover, Nashua and Rochester.

Meanwhile, Unitil had 5,600 customers in the dark. Virtually all of Danville is without power, as well as half of Kingston and a third of Unitil customers in Chichester.

• Storm Blog - Latest updates as NH braces for Hurricane Sandy

Power companies warned this morning that once winds top 35 mph, restoration efforts will have to cease because bucket trucks cannot operate safely in such conditions.

“The men can't get out and begin restoring power until it's safe to do so,” said PSNH spokesman Martin Murray.

Meanwhile, Gov. John Lynch declared a state of emergency this morning and urged employers to send workers home early enough that roads will be cleared by 3 p.m. He said people should avoid travel after 3 p.m., but did not order it.

Lynch sent non-essential state workers home, as did Manchester city government and the New Hampshire court system. The four Simon malls in New Hampshire, including those in Manchester and Salem, will close at 3 p.m. the company said.

And Amtrak closed its Downeaster commuter train, which runs through the Seacoast, around 2 p.m. and said its two earliest trains won't make runs on Tuesday. State transportation officials warned about possible flooding on Route 1A in Hampton.

Fierce winds and flooding were expected along hundreds of miles of the Atlantic coast, and heavy snows were forecast farther inland at higher elevations. U.S. stock markets closed for the first time since the attacks of September 11, 2001, the government in Washington shut down and school was cancelled up and down the East Coast.

Along Sandy's path, about 150,000 customers were without power by midday and millions more could lose electricity.

“This is going to be a big and powerful storm and all across the Eastern Seaboard I think everybody is taking the appropriate preparations,” President Barack Obama said at the White House.

Reuters reported that the storm will move ashore near Atlantic City, N.J., and National Weather Service maps show its stronger elements missing the Granite State.

Yet, preparations are in place. The state Emergency Operations Center went to the second highest status of Level 3 this morning, and 100 New Hampshire National Guard soldiers were activated and divided among armories in Manchester, Plymouth and the Pease air base.

“With anticipated high winds and heavy rain we are asking people to stay off the roads this afternoon, particularly after 3:00,” Lynch said in a statement.

“Water in the roadways, flying debris and downed power lines are all possible because of the severity of this storm, which is why we are urging people stay off the roads unless absolutely necessary.”

The Weather Service said that wind gusts of 55 to 60 mph will hit the state starting this afternoon; sustained winds will be 25 to 40 mph, depending on location. The strongest are expected for the coast, where storm surges are expected to damaged coastal property.

Raid showers are expected to last through Tuesday, and flooding is expected for eastern slopes of hills and mountains.

James Van Dongen, spokesman for the Emergency Operations Center, said flashfloods are the biggest concern. Small streams and city streets could quickly become overwhelmed by a downpour, he said.

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A list of school cancellations can be found here. Many communities have also rescheduled trick-or-treat times; those can be found at NewHampshire.com. A full list of recommended steps residents can take to prepare for the storm is available online at www.nh.gov/readynh/.