Washington's famed cherry blossoms, one of the U.S. capital's major tourist attractions, were badly damaged by this week's late-season winter storm, the National Park Service said on Wednesday.

Damaged blooms could cut into the tens of thousands of tourists who flock to enjoy the pink-and-white trees that make Washington's Cherry Blossom Festival one of the biggest U.S. springtime parties.

"The number of cherry trees that reach the blossom stage may be reduced as a result of the recent cold temperatures," the National Park Service said in a statement.

Blossoms at earlier stages of bloom will be forced open over the next day or two to determine if they have been harmed, the agency said.

Peak bloom for the Yoshino cherry trees, the most abundant variety, is expected between March 19 and 22. Washington's Cherry Blossom Festival opens on March 25 and runs through April 8.

Horticulturists who checked some of the thousands of cherry trees that line the city's Tidal Basin found widespread damage in blossoms that had reached the fifth of six stages in the bloom cycle, the Park Service said.

The cherry trees were a gift from Japan to Washington in 1912 to honor the friendship between the two countries.

Temperatures in the Washington area fell to 22 Fahrenheit (minus 5 Celsius) early on Wednesday as a winter storm pummeled the Northeast and Middle Atlantic states with high winds, snow and temperatures well below average.

Temperatures remained below 24F (minus 4C), when 90 percent of exposed blooms can be affected, for at least five hours, the Park Service said. Similar temperatures were expected for Wednesday and Thursday nights.

The National Park Service last week moved back its prediction for peak bloom. It previously had forecast the peak bloom for March 14-17, following the warmest February in Washington on record. The earliest peak bloom on record is March 15.