2026 Allergy Forecast: When will pollen be bad across the US?

Pollen is already ramping up in parts of the South and West. Here’s when tree, grass and weed pollen will spike — and which regions will have the highest levels this year.

For millions of Americans, spring doesn’t just mean warmer days and blooming flowers. It also means sneezing, itchy eyes and constant allergy medication.

So, when will pollen be bad this year? The answer depends on where you live and what kind of pollen triggers your symptoms. Tree pollen is already ramping up in parts of the South and West. Grass pollen will spike later in spring and early summer. Weed pollen could bring an intense late-season surge.

How weather affects pollen season

Temperature, rainfall, wind and springtime frosts all influence how much pollen ends up in the air. Warmer ground temperatures allow plants and trees to produce pollen more easily. Heavy rain can temporarily wash pollen out of the air, but a few dry days afterward often lead to a sharp spike. Wind can carry pollen hundreds of miles. Frost can briefly suppress pollen, only to intensify it later in the season.

Here is AccuWeather’s complete breakdown of the 2026 U.S. allergy forecast:

Tree Pollen: Early start in the South, intense bursts in the Ohio Valley

Tree pollen season has already begun across Southern California, southern Arizona and much of the Gulf Coast. As temperatures rise, pollen levels will climb northward through spring.

The Ohio Valley is expected to be one of the hardest-hit regions this year, with periods of exceptionally high tree pollen, especially after spring rainfall.

“A later frost can help short-term pollen with lowering the tree pollen for a short time, but also increase pollen later in the season and make it more intense,” said AccuWeather Senior Meteorologist Alan Reppert.

The frost dynamic is important. A late-spring frost can reduce pollen briefly, but levels often rebound later in the season. “Most early-season tree pollen-producing trees, such as Juniper and Alder trees, can be hit much worse [by frost] than late-season trees, such as Birch, Maple and Pine trees,” Reppert explained.

In the Pacific Northwest, tree pollen is expected to start earlier than typical and remain elevated for several weeks. Dramatically high levels are possible in Portland, Oregon, and Seattle.

Across the Plains, tree-pollen season may start more slowly than usual. However, residents should prepare for a few days of exceptionally high levels before counts drop off quickly. Parts of New England may have lower-than-average tree pollen this season due to a colder start to the year and less rainfall than typical.

Grass Pollen: Northern spike, uneven season in the South

Grass pollen typically ramps up as tree pollen fades, and this year it may spike early across the northern Plains and into the Great Lakes.

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

Grass responds quickly to moisture and warmth. After a soaking rain, it can grow rapidly and pollen levels can jump just as quickly.

Texas may experience above-average grass pollen for a few weeks, though the season could be shorter-lived compared to northern areas.

Along the Gulf Coast, rain returning to more typical levels, combined with a drier start to summer, may help keep grass pollen below average overall. Frequent, heavier rainfall can wash pollen out of the air, reducing sustained high levels.

In the Northwest, hot and dry weather is expected to keep grass pollen levels below average for much of the season. However, any rainfall could trigger a short-lived spike lasting a few days.

Weed Pollen: Intense in the Rockies, lower in parts of the East

Weed pollen is often associated with ragweed, but it also includes thistle, sagebrush and mugwort. It typically peaks later in summer and into early fall, dropping off after the first hard freeze.

“A combination of higher rainfall and a longer period until cold weather comes into the Rockies could make for an intense weed-pollen season, but ending a bit earlier than typical,” Reppert explained.

In contrast, cooler weather across eastern Texas through Kentucky and Alabama is expected to limit weed pollen levels.

Along coastal Oregon and Washington, repeated storm systems should provide enough moisture for weeds to grow. However, rainfall may occur often enough to wash pollen out of the air before it builds to extreme levels.

In the Northeast, a lack of rainfall early in weed season, combined with temperatures dropping more quickly, may limit pollen levels overall. Still, any rain event could cause a brief spike lasting several days.

How to reduce exposure during peak pollen days

Even with a forecast in hand, managing allergies often comes down to preparation:

•Limit time outdoors in the early morning through early afternoon, when pollen production is typically highest.
•Change clothes and shower after spending extended time outside.
•Use high-efficiency air filters and keep windows closed during peak days.
•Consider starting allergy medication before pollen levels surge.

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