Forecaster AccuWeather released a report on Thursday projecting high levels of weed and grass pollen across more than two dozen eastern and midwestern U.S. states this fall. The report attributes the expected surge to a combination of warm overnight temperatures and ample moisture. Meteorologists noted that while grass pollen typically diminishes in August and September, current weather patterns may sustain elevated levels in specific regions.
The forecast follows long-term data from the non-profit Climate Central, which found that nearly 180 U.S. cities now experience their first freeze an average of 12 days later than in the early 1970s. According to the American College of Allergy, Asthma and Immunology, these shifting climate patterns contribute to plants blooming earlier and producing greater quantities of pollen. AccuWeather meteorologists stated in March that the allergy season in the United States is expanding at both its beginning and end.
Specific metropolitan areas, including New York City, Philadelphia, Chicago, and Detroit, are predicted to see the highest levels of grass pollen. Meanwhile, weed pollen levels—primarily driven by ragweed—are expected to remain high into October across the Southeast and southern Rockies. Cities such as Atlanta, Nashville, Denver, and Salt Lake City are among those projected to experience the most significant impact from weed pollen this season.
The scale of the impact is documented across more than two dozen states, where residents may face increased costs for over-the-counter treatments like decongestants, nose sprays, and eye drops. Health experts also suggest lifestyle changes to manage the surge, including changing clothes after spending time outdoors and staying inside during high-pollen periods. In more severe cases, patients may seek medical consultation for allergy vaccines to decrease sensitivity, a process often considered a final option for treatment.
The persistence of pollen into late fall is linked to a lack of frost, which usually kills ragweed. Because the first freeze is occurring later in the year for 179 cities, the window for pollen production is physically longer than in previous decades. This trend sets a precedent for a shifting environmental calendar that requires healthcare providers and residents to adjust their seasonal preparations. The current weed pollen levels are expected to remain elevated until the first frost occurs in each respective region.