This April 10, 2013, file photo shows visitors walking along the Tidal Basin in Washington to enjoy the cherry blossom trees in full bloom.

WASHINGTON - It's been a long, snowy winter, but Washington's fabled cherry blossom trees are a hardy bunch and their blooming is right around the corner.

The famous trees are expected to bring the first sure sign of spring April 8-12, when they're predicted to reach peak bloom, the National Park Service said Tuesday.

"Relax and let Mother Nature take her course," said James Perry, chief of resource management for the National Park Service "This has not been the coldest winter on record or the snowiest. These trees have been around for 102 years, so we know pretty well how they're going to react."

The weather in March will be the most critical factor for the trees' blooming period, he said.

This year's flowers could come slightly later than last year and later than the average bloom date of April 4. Last year's blossoms were delayed by cold weather. The latest the trees have ever bloomed is April 18, Perry said.

About 70 percent of the trees around the Tidal Basin must be blossoming with pink and white flowers for the park service to declare peak bloom. Tree workers will be looking for the first sign of green buds, monitoring the weather forecast and reviewing historical records to update Perry's prediction because the projection is not an exact science, he said.

"The colder it is, the slower the process will be," he said. But there hasn't been any significant damage from the recent snow and ice, he said.

"The buds are naturally protected within the trees during the winter," Perry said. "That's a dormant phase for the development of the trees."

Perry made the flourishing prediction as organizers announced plans Tuesday for this year's National Cherry Blossom Festival, one of the nation's biggest springtime parties. It's scheduled to run from March 20-April 13 with events permeating around the city to celebrate the trees and Japanese culture. About 1.5 million people enjoyed the pink and white blooms last year.

This year marks the 102nd anniversary of the gift of the cherry blossom trees from Japan as a symbol of friendship with the United States.

This year's festival includes a fitness theme with free exercise sessions planned around the city's monuments. There is also a new water shuttle service to the Tidal Basin from the Georgetown waterfront, a new hop-on, hop-off bus tour and a Japanese film festival for the first time.

Washington's restaurants plan special menus, city buildings will be lit in a dazzling pink and hotels are offering more specials for visitors this year, organizers said. Some signature events associated with the cherry blossoms include a Japanese street festival, a kite festival and a parade on Constitution Avenue.