‘More pollen, more often’: Weather changes, warmer temperatures taking their toll on allergy sufferers

Seasonal allergies are getting worse across the U.S. as warmer temperatures and changing precipitation patterns produce longer growing seasons and more high-pollen days.

That is according to the 2026 U.S. Allergy Forecast from AccuWeather.

“The data is clear, and millions of seasonal allergy sufferers have noticed the changes. The seasonal allergy season in America is expanding at both ends,” said AccuWeather Climate Expert and Senior Meteorologist Brett Anderson. “Milder winters and warmer springs are allowing the growing season to start earlier in many regions. Later frost dates mean the allergy season is ending later in many places. When warmth and moisture align, trees, grass and weeds can produce more pollen more often.”

A climate study released by AccuWeather earlier this year found average temperatures have increased 0.5 degrees Fahrenheit per decade the past 70 years.

Changing precipitation patterns are also contributing to higher pollen and more allergy days, according to the weather forecaster. AccuWeater’s climate study found average annual rainfall has decreased 2.7% since 1995, but there are more extreme weather events.

“The frequency of rainfall amounts greater than 4 inches in a 24-hour period have actually increased by 70%. Likewise, heavy rainfall amounts greater than 2 inches within a 24-hour period have increased by 23%,” according to an announcement from AccuWeather.

“Longer growing seasons and more intense rainfall are creating conditions that can worsen seasonal allergies over time,” Anderson said.

He said warmer temperatures increase pollen production from trees, grasses and weeds. “This is a concerning trend for millions of Americans who struggle with seasonal allergies,” Anderson said.

According to the U.S. Centers for Disease Control (CDC) and other public health groups, 1 in 3 American adults and 1 in 4 American kids deal with seasonal allergies.

AccuWeather projects an early start to tree pollen season, with the Ohio Valley region and the Pacific Northwest forecasted with the highest levels. Seattle and Portland could see “dramatically high pollen levels,” according to the allergy forecast.

The weather group said late frosts could forestall pollen production by trees and other plants. But that can also mean more intense pollen and allergy days later in the spring.

“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,” AccuWeather Senior Meteorologist and allergy expert Alan Reppert said. “Early bloomers like juniper and alder trees tend to be hit harder by a late frost, while later-blooming trees such as birch, maple and pine are less affected.”

Midwestern cities such as Minneapolis, Chicago and St. Louis as well as Texas could see above-average grass pollen levels.

“A combination of above-average rainfall and some warmer weather will bring much higher grass pollen levels,” Reppert said.

Drought and dry conditions in Florida, the Gulf Coast and Southern states could keep grass pollen levels for those areas low this spring and into the summer.

Weed pollen is expected to be at high levels in Rocky Mountains states because of warming climate trends. New England, Texas and parts of the south could see lower pollen from ragweed, thistle and other weeds because of drier conditions.

In the Pacific Northwest, storm activity will bring plenty of weeds but significant rainfall can wash away the pollen, according to AccuWeather’s forecasters.

“Weather conditions in your neighborhood and even hundreds of miles away can significantly influence pollen levels and allergy symptoms,” Reppert said. “Temperature and rainfall determine how much pollen is released and how quickly levels spike. Heavy rain can temporarily clear the air, but just a few dry, breezy days can send counts surging. Strong winds can carry pollen dozens to hundreds of miles, lifting it thousands of feet into the atmosphere before it settles back to the ground.”