Ernesto weakened to a tropical depression Wednesday as it crawled northward through Florida, dropping locally heavy rain but causing little damage. It was on a track toward the Carolinas, where National Guard troops were mobilized as a precaution.

By early afternoon, the storm's top sustained wind had slowed to 35 mph, 4 mph below tropical storm strength, and little change was expected while the system remained over land, the National Hurricane Center said.

The heart of the storm was expected to move off Florida's northeast coast and into the Atlantic, where it could regain some of its strength before reaching the Carolinas.

Check the National Hurricane Center's forecast to monitor Tropical Storm Ernesto.

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A tropical storm warning remained in effect from Sebastian about halfway up Florida's east coast to Cape Fear, N.C. Warnings were canceled for the southern part of Florida, including Miami, and all hurricane watches were discontinued.

North Carolina Gov. Mike Easley on Wednesday activated National Guard troops and the State Emergency Response Team to prepare for possible flooding and power outages.

"Ernesto should not be a major event for North Carolina, but it is still important that citizens be prepared," Easley said.

South Carolina Gov. Mark Sanford announced Tuesday that nearly 250 National Guard would be mobilized there to help direct traffic if evacuations were ordered.

"The best-laid plans can be disrupted by Mother Nature, in the event this storm were to stall out over the warm waters of the Gulf Stream and intensify," Sanford said.

Some South Carolina counties planned to open shelters for residents of low-lying areas, mobile homes or beachfront areas who wanted to voluntarily evacuate. Charleston County schools operated on a shortened schedule Wednesday although officials made no immediate decision about closing Thursday.

In northwest Pennsylvania, crews worried about rain from the storm reaching a damaged dam in Polk planned emergency repairs. The dam overflowed Tuesday after more than 3 inches of rain fell, causing some erosion and flooding about 50 homes. The dam regulates water flow into Sandy Creek, a tributary of the Allegheny River.

At 2 p.m. EDT, the remnants of Ernesto were centered about 60 miles southwest of Vero Beach, moving north at about 10 mph.

Ernesto lost much of its punch crossing eastern Cuba and made landfall late Tuesday on Plantation Key with 45 mph wind — far from the 74 mph threshold for a hurricane that Ernesto briefly met Sunday.

"It was the little train that couldn't," said David Rudduck of the American Red Cross.

State emergency response team chief David Halstead said initial reports indicated Ernesto was a relatively minor storm when it went through the Keys. But he cautioned that full damage assessments weren't likely to be completed until later in the day, when there could still be problems such as fallen power lines and road flooding.

Visitors had been ordered to leave the Keys before Ernesto arrived, but they were being allowed to return as of noon Wednesday for the busy Labor Day weekend.

Parts of Florida got drenching rain, including about 2 inches at Fort Lauderdale by midmorning.

As much as 7 inches of rain was possible in North Carolina from the Raleigh-Durham area to the coast, the governor said. "We know this is going to be a water event," Easley said.

However, the rain could be beneficial for parts of North Carolina. "The ground is dry, the streams are low and the reservoirs are down," said state climatologist Ryan Boyles.

The storm initially prompted NASA to start moving the space shuttle to its assembly building for protection, but NASA later reversed course and sent it back to the launch pad.

Accidents on rain-slickened expressways killed at least two people in Florida on Tuesday. Ernesto also killed at least two people in Haiti.

About 6,800 Florida Power & Light customers lost electricity at one point, but most power was quickly restored. More than 3 million customers had lost power after Hurricane Wilma last year.