With tree pollen levels climbing in much of the country as spring nears, people with seasonal allergies may feel that symptoms like sneezing, coughing, and watery eyes last longer than ever. That’s because allergy season has grown longer throughout the United States over the past several decades, according to new research.
An analysis released this month from the nonprofit research group Climate Central shows that the frost-free growing season has extended by an average of 21 days since 1970 in at least 173 cities.
“Over the last 50 years or so, the time between the last freeze and the first freeze has gotten longer, so there’s essentially a longer growing season when plants generate the pollen that causes allergies,” says Kristy Dahl, PhD, vice president for science at Climate Central.
Not only is allergy season lengthening, the amount of pollen being put out is about 20 percent greater, too, which can make allergy symptoms more severe, adds Dr. Dahl.
Allergy Season Kicks Off Early in 2026
Allergy season has already started for many Americans, as warm spring weather arrives earlier than usual in some regions of the United States.
The arrival of tree pollen coincides with the first leafing and blooming of the season — and it’s coming three to five weeks sooner than expected in Colorado, Kansas, and the Northern Great Plains, including parts of Montana, Nebraska, North Dakota, South Dakota, and Wyoming, according to USA National Phenology Network, a scientific research group that collaborates with Climate Central.
Tracking also indicates that this initial spread of pollen has started 10 to 20 days early along the Gulf Coast and much of Oklahoma. The AccuWeather Allergy Forecast shows that tree pollen season has begun across southern California and southern Arizona as well.
Some Regions Hit Harder Than Others
The changes in allergy season vary depending on where you live. A few regions in the United States are experiencing a pause in the arrival of spring due to colder temperatures earlier this year. The Phenology Network notes that spring is one to two weeks late in Georgia, the Carolinas, and Virginia.
A cold start to the year in the eastern part of the country may keep tree pollen levels low in that region until later in the spring, according to the AccuWeather Forecast. The weather service warns, however, that a late spring frost may only provide temporary pollen relief, as levels can return intensely later in the season. After the spring rainfalls, AccuWeather expects the Ohio Valley to be one of the hardest-hit regions this year.
Spring weather is already heading north at a steady clip in the western United States, arriving about a month early in Billings, Montana, and 10 days early in St. Louis.
“We’re seeing some of the biggest increases in pollen in the Northwest where the growing season has expanded by 31 days since 1970,” says Dahl. “It’s a pretty warm climate there to begin with, so it’s easier to get to frost-free conditions.”
Climate Change Is Largely to Blame
As to what’s causing this shift, Dahl points to climate change.
“It’s a clear signal of a warming world, driven by carbon pollution,” she says. “As we humans add carbon dioxide to the atmosphere by burning more fossil fuels, that becomes like food for plants, and they’re able to produce more pollen.”
She urges efforts to put a cap on global warming by cutting emissions that trap gasses like carbon dioxide.
“One of the most effective ways to do this is by gradually weaning ourselves off of fossil fuels like coal, oil, and gas,” she says. “If we care about our long term health and want to see allergy seasons minimized, then prioritizing cuts to emissions would help to ensure that kind of future.”
Getting Ready for the Pollen Storm
“This is going to be a really tough time for those with allergies,” says Juanita Mora, MD, an allergist with the Chicago Allergy Center and a member of the board of directors at the American Lung Association. “People need to be prepared to get their allergies and asthma under good control as the pollen really hits.”
For those who suffer the most from allergies and asthma, Nana Mireku MD, a pediatric allergist with TexasAllergyMD and a spokesperson for the American College of Allergy, Asthma, and Immunology, advises starting medications (antihistamines, nose sprays, inhalers) two to three weeks before allergy season in their region begins.
“These medications work best when they are already active in your system before pollen levels peak,” she says.
Drs. Mora and Mireku offer a few tips for managing allergies as the season revs up:
- Sleep with windows closed. “If you sleep with windows open, pollen comes in, and you’re going to wake up super congested with symptoms like swollen eyes,” says Mora. “Consider driving with windows closed, too.”
- Wash after being outside. If you’ve been outside for an extended period, Mora advises taking a shower and changing your clothes.
- Monitor pollen counts. Check local allergy forecasts and limit outdoor exposure when pollen counts are high.
- Get evaluated by a board-certified allergist. Allergy testing can identify exactly what triggers your symptoms, allowing for targeted treatment, says Mireku.
- Use appropriate medications. Saline rinses, nasal steroid sprays, and antihistamines can significantly reduce daily symptoms. Check the date on products to make sure they are not expired.
- Consider allergen immunotherapy. Allergy shots or sublingual tablets and drops can gradually desensitize the immune system and provide long-term relief.
“Longer allergy seasons are more than just an inconvenience — for many individuals, they can be debilitating and may worsen other allergic conditions such as asthma and eczema,” says Mireku.
And allergy miseries don’t end after the spring. As tree pollen subsides, grass pollen will ramp up, and then ragweed storms will be coming during the fall.
“Expect a long stretch of sneezing, itchy eyes, and coughing ahead,” says Mora.
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