Sneezy in Seattle: How our allergy seasons are getting worse

It's not just you. Allergy season isn't the same as it used to be.

Climate change caused by fossil fuels is heating up the planet. In the Northwest, winters have warmed and summers have gotten hotter on average. This has lengthened growing seasons across the U.S., meaning plants have more time to bloom and release eye-watering and sneeze-inducing pollen.

A new Climate Central analysis of data from the National Oceanic and Atmospheric Administration estimates that allergy season in the Northwest, including Washington, Oregon and Idaho, has increased by 31 days since 1970, the most out of any other U.S. region.

While other cities in the region have seen longer allergy seasons, the Seattle and Tacoma area's has increased by 12 days.

More changes in precipitation and temperature could alter the intensity and timing of how plants bloom - and what species thrive.

How is allergy season changing?

The Washington State Department of Health refers to these sneezy months of the year as pollen season," highlighting the allergens that can rev up our immune systems and cause cold-like symptoms.

While each year varies, the state says pollen season in Washington is starting 20 days earlier and lasting almost a month longer compared to three decades ago.

The Climate Central analysis measures allergy season by the number of days between the first and last day temperatures are above freezing and found the Northwest's has grown by 31 days compared to over five decades ago.

The increases are largest in cities farther south and on the eastern side of the state. Cities like Spokane and Yakima in Washington, and Portland and Eugene in Oregon, saw the largest increases in the growing season since 1970 of between 30 and 41 days, according to the analysis.

In the Seattle and Tacoma area, the freeze-free growing season has increased by around 12 days.

Can things get worse?

It's not fully clear how climate change may impact the allergy season as a whole in Seattle.

In Western Washington, allergy season is primarily made up of tree pollen that is released first, followed by grass pollen in the middle of summer and then weeds at the end of the growing season. These plants all rely on cues from the sun, temperature and rain to determine when to bloom and release.

While there are plants that may go dormant and release less pollen, other plants might release even more, said Cecilia Welch, a climate and water epidemiologist with the Washington Department of Health.

"It's hard to know how the plant populations are going to change and how their pollen generation triggers will change," she said.

However, research indicates that human-caused climate change has already exacerbated North America's pollen seasons and respiratory health impacts are likely to worsen in the coming decades.

There is also concern and research indicating that ragweed, a "huge allergen across the country, may eventually gain a foothold in the Western Washington area, Welch said.

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This story was originally published April 20, 2026 at 6:42 AM.