Rising Ragweed Pollen: Why Fall Allergies in the U.S. Are Getting Worse

September 23, 2025
|In Blog, Patients
|By United Allergy Services

Every fall, ragweed pollen has long been a familiar culprit behind sneezing, congestion, and itchy eyes. But lately, it’s not just the symptoms that are changing—it’s the season itself. Rising ragweed pollen levels are making allergy season longer, more intense, and harder to escape.

What the Data Show

  • Since about 1995, the ragweed pollen season has lengthened in 10 out of 11 studied locations in the central U.S. and Canada. In northern areas, the increase has been especially large: Winnipeg has seen the season grow by approximately 25 days, Fargo by 21 days, and Minneapolis by 18 days.
  • Research also finds that warmer temperatures and higher carbon dioxide levels lead ragweed (and other seasonal allergens) to produce more pollen and to start earlier and end later.
  • A recent investigation in Michigan linked high ragweed pollen exposure to increased respiratory mortality in older adults; the effect could persist for up to two weeks after exposure.

How This Affects Americans in the Fall

  • Longer exposure: Ragweed pollen, which traditionally peaks in mid-September and lasts through October in many regions, is now beginning earlier and lingering later into fall.
  • More severe symptoms: With more pollen in the air over a longer time, people with seasonal allergic rhinitis (“hay fever”) and asthma are experiencing worse flare-ups.
  • Broader impacts on health and well-being: Beyond just discomfort, there are effects on sleep, school and work productivity, increased healthcare visits, and elevated risks for those with chronic respiratory conditions.

What’s Driving the Increase?

  • Climate change: Warmer average temperatures delay the first frost in fall, extend the growing season for ragweed, and allow for earlier flowering in spring.
  • Higher CO₂ concentrations: Plants respond by producing more pollen, and sometimes pollen that is more allergenic.
  • Urban heat islands and environmental changes: Cities tend to stay warmer, which can magnify these effects. Land disturbance, changes in land use, and soil exposure contribute to ragweed spread.

What Can Be Done

  • Awareness and monitoring: Check daily pollen counts; be alert for early season symptoms.
  • Preventive measures: Starting allergy medications before symptoms flare can help. Using air filtration, keeping windows closed on high-pollen days, and rinsing off pollen after outdoor exposure all help.
  • Seek professional help: For people with severe allergy or asthma symptoms, getting evaluated by a medical provider may be important—immunotherapy might reduce the severity long-term.
  • Find a provider near you: If you think you might benefit from allergy testing or long-term treatment, you can use this tool:
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Takeaway

Fall allergies aren’t what they used to be. With ragweed pollen seasons getting longer and stronger, more Americans are suffering for more of the year. But by understanding what’s changed, staying informed, taking preventive steps, and connecting with medical providers when needed, it’s possible to reduce the burden and breathe a little easier.

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