No single state holds the official title for worst pollen, but the data consistently points to a cluster of states in the South Central U.S. as the most challenging places for allergy sufferers. Kansas, Oklahoma, Louisiana, Tennessee, and Arkansas dominate the top of national rankings, with cities in those states recording the highest combination of pollen counts, medication use, and allergy-related medical visits.
The Worst States for Pollen Allergies
The Asthma and Allergy Foundation of America publishes an annual “Allergy Capitals” report that ranks the 100 most populated metro areas based on pollen levels, allergy medication usage, and the number of allergy specialists available. The 2025 report paints a clear geographic picture. Wichita, Kansas took the top spot, followed by New Orleans, Louisiana. Oklahoma placed two cities in the top five (Oklahoma City at third, Tulsa at fourth), while Memphis, Tennessee ranked fifth and Little Rock, Arkansas sixth.
The Southeast also features heavily. Raleigh and Greensboro in North Carolina, Richmond in Virginia, and Greenville in South Carolina all landed in the top 10. If you’re looking at statewide patterns rather than individual cities, Oklahoma and North Carolina each placed multiple metros in the worst category, making them especially rough for anyone with seasonal allergies.
Why These States Are So Bad
Geography and climate explain most of the pattern. The states topping the list share a few key features: long growing seasons, warm and humid air, and diverse plant life that produces overlapping waves of pollen throughout the year. In the South Central region, tree pollen can start as early as February, grass pollen peaks in late spring and early summer, and ragweed takes over from August through October. That means residents in states like Oklahoma or Arkansas can face eight or nine months of elevated pollen exposure with very little relief.
Ragweed is the single biggest driver of fall allergies across much of the country. It starts releasing pollen around August and peaks in mid-September, often lasting through October. A single ragweed plant can release a billion grains of pollen per season, and the lightweight grains travel hundreds of miles on the wind. States in the Mississippi River corridor and Great Plains are especially saturated with ragweed, which is one reason Kansas, Oklahoma, and Louisiana rank so consistently high.
What Pollen Counts Actually Mean
Pollen levels are measured in grains per cubic meter of air, and the thresholds vary depending on the type of plant. For tree pollen, anything above 90 grains per cubic meter is considered high, and counts above 1,500 are classified as very high. Grass pollen hits the high category at just 20 grains per cubic meter. Weed pollen, including ragweed, is considered high above 50 grains.
These numbers matter because they correlate directly with health outcomes. Research published in the Annals of Emergency Medicine found that a meaningful increase in oak or grass pollen counts was associated with roughly a 3% rise in daily emergency department visits for asthma. That percentage might sound small, but across a metro area over an entire pollen season, it translates to thousands of extra ER visits and significant strain on both patients and hospitals.
Pollen Seasons Are Getting Longer
If your allergies feel worse than they did a decade ago, you’re not imagining it. A 2021 study found that North American pollen seasons lengthened by an average of 20 days between 1990 and 2018, driven primarily by rising temperatures from climate change. Warmer springs mean trees start releasing pollen earlier, and warmer falls mean ragweed and other weeds keep producing later into the year. Higher concentrations of carbon dioxide also cause plants to produce more pollen per plant.
This trend hits the already worst-affected states hardest. Cities in the South and Midwest that already had long growing seasons are seeing those seasons stretch even further. Climate Central’s analysis of 172 U.S. cities confirmed that the overlap between longer frost-free periods and longer allergy seasons is tightening, leaving fewer weeks of genuinely low-pollen air in the places that need it most.
Urban Planning Makes Some Cities Worse
Your city’s landscaping choices also play a role. For decades, urban planners favored planting male trees because they don’t produce fruit or seed pods that create litter on sidewalks. The tradeoff is that male trees are the ones releasing pollen. This practice, sometimes called “botanical sexism,” has been blamed for increasing airborne pollen in cities. However, research from New York complicates that narrative somewhat: scientists tracking airborne pollen found that 71% of it came from just four types of trees, three of which produce pollen regardless of sex (they carry both male and female parts on the same tree). So while planting choices matter, the dominant pollen sources in most cities aren’t the ones being selectively cloned for gender.
Still, heavily landscaped cities in warm states tend to have higher local pollen counts than rural areas with the same vegetation, because the concentration of ornamental trees adds to the baseline pollen from surrounding forests and fields.
The Financial Cost of Living in High-Pollen States
Allergies aren’t just uncomfortable. They’re expensive. Research from the American Academy of Allergy, Asthma, and Immunology found that a single poorly controlled week of allergic rhinitis costs a median of about $508 per person in lost productivity alone. That figure doesn’t include medication, doctor visits, or the compounding effect of months of symptoms. For someone living in Wichita or Oklahoma City, where pollen seasons can stretch most of the year, the annual financial hit from allergies can easily run into the thousands.
Best and Worst Months by Region
If you live in one of the worst states for pollen, the timing of your symptoms depends on what you’re allergic to. Tree pollen is the first wave, typically peaking from March through May across the South and starting slightly later in northern states. Grass pollen follows from May through July. Ragweed dominates August through October. In states like Oklahoma, Arkansas, and Tennessee, these waves overlap enough that April through October is essentially one continuous allergy season.
The safest months in high-pollen states are typically December through February, when most plants are dormant. If you’re considering a move and allergies are a major factor, the western mountain states and parts of the Pacific Northwest generally report lower pollen counts, though no region is entirely pollen-free. Coastal areas with consistent onshore breezes also tend to have lower concentrations, since wind off the ocean carries cleaner air inland.