How Does The Pollen Count Drop Without Rain To Wash It Away?

      In a previous post I discussed the recent jump in tree pollen count on March 27th to the 28th that went from 568 Grains/Cubic Meter to 2124 gr/cubic meter. What I didn’t touch on though was the notable drop in the count the next day on March 29th when it fell back down to 350 gr/cubic meter. This significant drop left me not just scratching my eyes, but also my head. I went back and took a look at the official records from the all the area airports and found that the only recorded rain on March 28th was .03” at both BWI and Dulles and .01” at Reagan National. So suffice to say while there were a few showers, they were very light and may have been just enough to briefly wet the roads at best. Certainly that was not enough rain to aid in cleaning the air and washing the pollen away. So what other factors could contribute to such a drop? To find the answer I went back to my friend Susan Kosisky at the US Army Centralized Allergen Extract Lab (U.S.A.C.A.E.L) and here’s what she had to say.

      “We like to say "Do a rain dance" help clear the air of all the pollen. Changes in temperature, humidity and even the amount of sunshine can also impact the amount of pollen that is released by our area tree species. As soon as the cooler air and clouds moved into the area, the pollen count did indeed drop. Warmer, dry days with plenty of sunshine and spring breezes facilitate the drying, cracking, release and dispersal of pollen from the anther sacs (pollen producing pouch). Cooler, cloudy weather (especially with dampness, higher humidity and rain) like we had at the end of last week and over the weekend slows up the release of pollen somewhat after a string of exceptionally warm sunny days.”

      Today’s report from the U.S.A.C.A.E.L for April 2nd finds that tree pollen remains high at 308 gr/cubic meter. However Susan also commented today that, “There is some good news on the horizon....some of the area oak trees are already dropping those brown wormy looking catkins (the flowering parts that release the pollen into the air) along curbsides. This is a good sign as some of the oaks have finished flowering and their pollen has been released for the season.”{ }

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      Some additional good news is that we do have a chance for a few showers in the forecast tomorrow mainly during the afternoon and evening. So consider yourself lucky if you happen to find yourself under one of those showers as it will help to wash some of that pollen out of the air.{ }

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