Washington’s famed cherry blossoms may peak over a shorter period this year, but bloom for a slightly longer time, the National Park Service said Wednesday, altering its original forecast of a few weeks earlier.

The Park Service said recent warm weather may accelerate the peak bloom, shortening it by several days, while chillier weather forecast this week may extend the overall blooming period.

This year’s peak bloom was originally expected to occur from March 29 to April 3, but Park Service horticulturist and cherry tree expert Rob DeFeo predicted Wednesday that it now could conclude by April 1.

Warmer temperatures tend to hasten the blooming process. Colder temperatures can slow it down, and DeFeo reported that the forecast chill this week could do just that.

The bulk of the trees, with their delicate pale pink blossoms, are clustered around the Tidal Basin.

Although some of the city’s Japanese cherry trees are already starting to bloom, the Park Service lists this year’s overall blooming period from March 26 to April 7.

The National Cherry Blossom Festival starts this weekend — kicking off with the annual opening family celebration Saturday at the National Building Museum and the Blossom Kite Festival on Sunday at the Washington Monument.

The blossom fest runs through April 10, with the annual parade April 9.

This year’s events are expected to be more muted than usual because of the earthquake and tsunami in Japan. A special “Stand With Japan” walk, sponsored by the festival, is scheduled for 6:30 p.m. Thursday, starting at the Sylvan Theater, south of the Washington Monument.