Tropical Storm Beryl hit the southeastern US coast at near-hurricane strength early Monday, toppling trees and downing power lines as it cast a shadow over the first big beach weekend of the summer.

At 0900 GMT, Beryl's center was located inland about 20 miles (300 kilometers) west of Jacksonville, Florida, the Miami-based National Hurricane Center reported.

After coming ashore near the Florida-Georgia state line, Beryl has become significantly weaker, packing maximum sustained winds of 50 miles (80 kilometers) per hour.

But although the center no longer predicted Beryl becoming a hurricane, it warned that "tropical storm wind gusts are possible elsewhere over northeastern Florida and southeastern Georgia today, particularly in rainbands."

With the storm moving towards the west at eight miles (13 kilometers) per hour, forecasters said it will move into southeast Georgia late Monday or Tuesday.

"Gradual weakening is expected to continue today, and Beryl is forecast to become a tropical depression tonight," the NHC said.

After the landfall, tropical storm warnings were lifted north of the Savannah River.

However, the NHC warned that a storm surge combined with a rising tide "will cause normally dry areas near the coast to be flooded by rising waters."

The storm was forecast to dump three to six inches (eight to 15 centimeters) of rain along the coast from northern Florida to southeastern North Carolina.

The storm struck during the long Memorial Day holiday weekend in which millions of Americans typically head for the beaches to celebrate the beginning of the summer season.

Jacksonville Mayor Alvin Brown signed an emergency declaration Sunday and urged residents to stay home and away from the beaches. He also announced the cancelation of all Memorial Day ceremonies scheduled for Monday as a precaution.

"Nothing is more important to me right now than safety," said Brown, addressing residents on local television. "Tropical Storm Beryl has potential to down power lines and cause flooding."

Storm winds have already damaged the windows at Jacksonville's Museum of Contemporary Art and knocked down trees in various parts of the city, The Florida Times-Union newspaper reported.

High winds knocked down trees and powerlines. About 38,000 customers in various areas in Jacksonville were without power, local media reports said.

The Mathews Bridge, one of the largest in the city, has been closed until further notice because of storm-related safety concerns, authorities said.

And the Jacksonville Aviation Authority said all airlines, except JetBlue and Delta, have canceled incoming and outgoing flights.

The US National Oceanic and Atmospheric Administration has meanwhile predicted a "near-normal" Atlantic hurricane season is likely this year.

The Atlantic hurricane region includes the northern Atlantic, the Caribbean Sea and the Gulf of Mexico.