AccuWeather meteorologists released their 2026 U.S. allergy forecast on March 4, warning that 29 states should expect pollen levels to exceed historical averages this year. As spring warmth expands northward, experts indicate that shifting storm tracks and rising temperatures are creating a volatile environment for allergy sufferers.
While the South and West are already seeing tree pollen activity, the coming weeks are expected to bring sharp swings in air quality across the rest of the country.
According to AccuWeather Senior Meteorologist Alan Reppert, local weather conditions and even distant wind patterns play a massive role in daily symptoms.
“Temperature and rainfall determine how much pollen is released and how quickly levels spike,” Reppert said. He noted that while heavy rain can temporarily wash the air clean, just a few dry and breezy days can cause counts to surge. Strong winds are also capable of carrying pollen thousands of feet into the air and transporting it hundreds of miles away.
The report highlights specific regional risks for tree, grass, and weed pollen. Tree pollen is already climbing in Southern California, Arizona, and the Gulf Coast. However, the Ohio Valley is projected to see the highest tree pollen levels this year, particularly after April rains.
In the Pacific Northwest, cities like Seattle and Portland may experience dramatically high levels as their season starts earlier than usual. Conversely, New England might see lower-than-average tree pollen due to a colder spring forecast.
Reppert explained that late-season frosts can complicate the timing, stating, “A late frost can lower tree pollen for a short time, but it can increase pollen later in the season and make it more intense.”
As the year progresses into June and July, grass pollen is expected to spike across the northern Plains and the Great Lakes. Above-average rainfall and warmth are likely to trigger high to extreme levels in Chicago, St. Louis, and Minneapolis.
In the Western U.S., the Rocky Mountains are bracing for an intense weed pollen season. “A combination of higher rainfall and a longer period until cold weather comes into the Rockies could make for an intense weed pollen season,” Reppert said, though he noted the season might end earlier than typical for that region.
Climate experts at AccuWeather point to a broader trend of expanding growing seasons. Data shows that U.S. temperatures have risen by an average of 0.5°F per decade over the last 70 years.
“The seasonal allergy season in America is expanding at both ends,” explained AccuWeather Climate Expert Brett Anderson. He attributed the change to milder winters and later frost dates, which allow plants to produce more pollen over a longer period.
Anderson also noted that rising carbon dioxide levels from fossil fuel emissions are contributing to increased pollen production, a trend he described as concerning for the millions of Americans living with seasonal allergies.
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