Sign up for CNN's Life, But Greener newsletter. Our limited newsletter series guides you on how to minimize your personal role in the climate crisis — and reduce your eco-anxiety.
(CNN)It's only early March, but the pollen floating around the air in the Southern and Eastern US is already eye-watering.
In Atlanta, the pollen count climbed to the "extremely high" range on Monday -- the earliest it has done so in 30 years of record-keeping, according to the Atlanta Allergy and Asthma physicians practice. By Tuesday, the tree pollen count had doubled.
Farther north in Washington, DC, the first "high" tree pollen count appeared a month ago on February 8, the Washington Post's Capital Weather Gang reported. At 487 grains per every cubic meter of air, it was the highest count on record so early in the season, Susan Kosisky, a chief microbiologist at the US Army Centralized Allergen Extract Lab, told the Post.
In short, pollen has exploded from plants much earlier than normal this year after an exceptionally warm February in the South and East. But these aren't isolated trends. As the planet warms, researchers say, allergy season is starting earlier and lasting longer.
A report released Wednesday by Climate Central, a nonprofit focused on climate news and research, analyzed how warmer temperatures have affected allergy season in 203 US cities since 1970. It found that on average, growing season -- the period between the last freeze in spring to the first freeze of fall -- is lasting 16 days longer in the Southeast, 15 days longer in the Northeast and 14 days longer in the South.
In the West, growing season is 27 days longer on average, Climate Central reported. Reno, Nevada, for example, has seen a shocking increase of 99 days.
Growing season in the US has lengthened by 15 days on average, according to a Climate Central analysis.
"Because of climate change, we're now seeing an earlier and longer growing season for plants, which of course make pollen, which is the enemy of many Americans that suffer from pollen allergies -- and mold allergies as well," Lauren Casey, a meteorologist with Climate Central, told CNN. "Pollen can also trigger an asthma attack, which of course is much more serious for people that suffer from asthma."
When plants reproduce, typically during the spring, many release tiny pollen grains that are carried by wind. The pollen grains are small enough to be inhaled, and some people's immune systems react very poorly to the miniscule particles.
More than 24 million people in the US have pollen-induced respiratory allergies like hay fever, according to the Centers for Disease Control and Prevention.