WASHINGTON — The cherry blossoms are peaking, and so is the traffic. As thousands head to the Tidal Basin and National Mall to see D.C.'s iconic trees in full bloom, traffic in and around the District is backing up fast—on roadways and underground.

Peak bloom occurs when 70% of the blossoms of the Yoshino cherry trees, the most common type along the Tidal Basin, are open. The National Park Service, which tracks the blooming of the trees each year, predicts peak bloom will be between March 28 and 31 this year.