Undated (AP) _ Flooding in New England forced people from their homes, washed away a historic covered bridge and damaged three dams Wednesday, while farmers in the South endured a third day of record cold that already had devastated some peach orchards.

Maine Gov. John R. McKernan Jr. declared a state of emergency, allowing application for federal aid and mobilization of the National Guard, as flooding described as the worst in a half century increased around the state.

''The water in a convenience store is right up to the ceiling, which I'd say is eight to nine feet off the ground, and it's still rising,'' regional police and fire dispatcher William Murray said of a store outside Plymouth, N.H.

The flooding was caused by melting snow and a storm bearing 50 mph wind and as much as 5 inches of rain that cut power to thousands Tuesday after dumping more than a foot of snow in the Ohio Valley.

On the Plains, Kansas National Guard helicopters hauled more hay to cattle snowbound by last week's back-to-back blizzards, and some roads were still blocked by drifts up to 15 feet high. Schools reopened Wednesday in adjacent areas of eastern Nebraska that were hard hit by the snow.

At least 27 deaths have been blamed on the weather since the first of the storms hit the Plains last week.

Low temperature records were broken or tied Wednesday in at least 40 cities from Texas to Florida and north to Maryland. Atlanta dipped to 27, toppling a record that had stood since 1919, and Macon, Ga., hit 29, its coldest on record for the entire month. Key West, Fla., the southernmost point in the continental United States, had a record 59.

Maine's Piscataquis River ripped away three gasoline storage tanks, each containing an estimated 10,000 gallons of fuel, in Dover-Foxcroft and carried them downstream, said Penobscot County deputy Ralph Holmes. He said a bridge downstream in Howland was closed as a precaution.

By early evening, state civil defense officials said sections of more than 125 roads had been closed as major rivers and streams in most areas of the state swirled far beyond their banks. State officials said it was too early to put a price tag on the damage.

At least 250 people were evacuated in Maine, including more than 100 moved from a nursing home in Canton by National Guard trucks, said David Brown, director of civil emergency preparedness.

A 75-foot section of earth washed away at the edge of a retaining wall near International Paper Co.'s hydroelectric dam in Livermore Falls, Maine, said IP Energy Superintendent Dick Brophy. He said there was no danger downstream.

A hydroelectric dam in the early stages of construction on the Androscoggin River at Lisbon ''is gone'' said a police officer who did not give his name. He said no evacuations had resulted.

A historic covered bridge over the Piscataquis River was washed away at Guilford, Maine. Central Maine Power Co. cut off power to the area, for fear that live electric lines running over other bridges would be snapped if the spans washed out.

In the state capital of Augusta, City Hall was evacuated and the Kennebec River was expected to crest at 23 feet above flood stage, five feet higher than during the record 1936 flood, the National Weather Service said.

A state game warden reported seeing a house floating down the river in Augusta, and in Wilton, a section of the firehouse was torn out by Wilson Stream and ''disappeared - it's gone downstream,'' said Town Manager Paul Soucie.

In central Connecticut, a dam of Meriden's Kenmere Reservoir broke late Tuesday as heavy rains pelted the state. The water rushed over a spillway and onto a golf course in Berlin, Conn.

People returned to their homes in the Kenmere Reservoir area Wednesday, after about 100 homes were evacuated before the 11 break. Residents and city officials said the dam may have been weakened because it had been under repair.

About 75 families were evacuated in Plymouth, N.H., Tuesday, as rivers and streams overflowed their banks. About 60 people were evacuated in Claremont, but they returned home Wednesday. Roads were closed in more than 60 places around New Hampshire, said Ken Jollimore of the state Civil Defense.

The Pemigewasset River rose to 14 feet above flood level in Plymouth, causing extensive damage to about a dozen businesses near the river in Holderness, authorities said.

The rain also was blamed for a school bus accident in Alton, N.H., that sent eight children to the hospital with minor injuries, and in Nashua, N.H., raging waters hampered a search for a person who witnesses said fell into the Nashua River and is presumed drowned.

About 30 families were forced from their homes in Island Pond, Vt.

In Rochester, Vt., Brian Bissonette found his expensive DeLorean car afloat. ''It's something they didn't include in the advertising,'' he said of the vehicle's buoyancy. ''Actually, they float quite nicely.''

Farmers in the South spread mulch, sprayed water, fired up smudge pots, tires and hay bales and called in helicopters to keep cold air from settling as temperatures plunged overnight.

Growers in the Hill Country of central Texas estimated as much as 80 percent of the area's $10 million peach crop may have been lost in the arctic air that froze new blossoms Sunday and Monday.

''It looks like we will be eating a lot of California peaches this year,'' said Kenneth Pape of Seguin, Texas.

In Florida, ''Alachua County farmers report extensive damage to beans and squash ... and a report from Ocala estimates that half of the watermelon crop may be lost,'' said state Agriculture Commissioner Doyle Conner.

In Alabama, ''the cold weather hurt us awful bad last night,'' said Dan Mims, extension agent in Chilton County, where 3,500 acres of peach orchards represents 70 percent of the state's crop. The county's growers lost 75 percent of their fruit to cold last year, and 85 percent in 1985.

Stormy weather has been blamed for two deaths each in Kentucky, Alabama and Pennsylvania, five in Ohio, four in Indiana, three in Kansas, one in Colorado, one in Massachusetts and seven in Nebraska.