WASHINGTON, March 26 (Xinhua) -- The cherry blossoms in Washington D.C. are expected to reach peak bloom a few days earlier than originally predicted.

The peak bloom will occur on April 1 this year, the U.S. National Park Service (NPS) tweeted on Tuesday. The prediction in March said it would reach peak bloom April 3-6.

"Determining the peak bloom date requires checking both the forecast and where the trees are in the blooming process," said the NPS, adding that the indicator tree is in full bloom and temperature forecasts are in the upper 70 degrees Fahrenheit (about 21 degrees Celsius) this weekend.

The cherry blossoms on Monday reached stage 4, or peduncle elongation, which, per the National Cherry Blossom Festival website, typically occurs between 5-10 days ahead of peak bloom.

The NPS said last year's cherry blossoms reached peak bloom on April 5. The average dates for peak bloom are April 3 and 4.

Peak bloom lasts for at least several days but can last up to two weeks if weather permits. The best time to visit the trees on the Tidal Basin, a partially man-made reservoir between the Potomac River and the U.S. capital, is 4-7 days after peak.

This year's annual National Cherry Blossom Festival is held from March 20-April 14.

According to the NPS, the peak bloom date is defined as the day when 70 percent of the Yoshino Cherry blossoms are open.

Peak bloom varies annually depending on weather conditions. The most likely time to reach peak bloom is between the last week of March and the first week of April.

Extraordinary warm or cool temperatures have resulted in peak bloom as early as March 15 (1990) and as late as April 18 (1958).