Update March 31, 2017: Come to the convention to sing and socialize, not look at cherry blossoms! A significant fraction of the Tidal Basin blossoms were damaged by the severe freeze in mid-March. Those not damaged reached "peak bloom" on March 25, according to the National Park Service. A live Webcam on March 31 showed a satisfying, better-than-expected display of bloom, which will probably not last much longer. Early American hymnody and psalmody last a lot longer than cherry blossoms.
The blooming of the famous and beautiful -- but transitory -- Yoshino cherry trees around the Tidal Basin and Jefferson Memorial in Washington, DC usually reaches a peak during the first week of April, although there is considerable variation from year to year. Singers attending the Potomac River Convention during its usual first-Sunday weekend in April usually are able to see the blossoms in at least partial bloom, and in some years are able to catch them in full bloom.
Starting in late February or March, the National Park Service horticulturist in charge of the trees issues predicted peak-bloom periods (see Web links below). The definition of "peak bloom prediction dates" seems to be poorly explained and may be misinterpreted by the media. (The term seems to mean the range of dates in which NPS predicts will fall the Peak Bloom Date (first day of at least 70% open blossoms). Some media may misinterpret this range of dates to mean the precise dates in which the blossoms will be at their peak.) It is best to visit the cherry blossoms very early in the morning or late in the afternoon or early evening, to avoid the crowds.
Other species of cherry trees, as well as flowers such as daffodils, are usually in bloom during this period also, providing multiple delights to those visiting Washington for the Potomac River Convention.
For latest information on blooming dates, consult the Bloom Watch Web page of the National Park Service.
The 2017 National Cherry Blossom Festival will take place from March 20 to April 16. Consult the Festival's Web site.