Propelled by mild temperatures, partial sunshine and gentle breezes, tree pollen levels have leaped to their highest level of the year. This is a “very high” count, according to Susan Kosisky, a microbiologist who directs the lab. Washington's peak tree pollen counts by year. “Many of our abundant tree pollen producers are also not quite at peak level concentrations, to include pine, birch, mulberry, sycamore and ash. Time series of 2019 tree pollen levels compared to average.

Source: Washington Post April 18, 2019 15:06 UTC