Is it allergy season in Oregon?

Oregon has a distinctly different pollen profile from the rest of the US. Alder — virtually unknown as an allergen in most states — is a major early-season trigger in western Oregon, releasing heavy pollen from January through March. Then comes the Willamette Valley's extraordinary grass season: the region grows roughly 60% of the world's grass seed, producing grass pollen counts that can be among the highest recorded anywhere in North America.

The Cascade Mountains create a dramatic divide in Oregon's climate and allergy patterns. West of the Cascades, the rainy maritime climate supports dense forests and the grass-farming Willamette Valley. East of the Cascades, the high desert is much drier with lower humidity, different plant communities, and generally lower overall pollen counts — though sagebrush weed pollen is notable in fall.

Willamette Valley

Eugene and Salem — global grass pollen epicenter

Eugene and Salem sit in the heart of the Willamette Valley's grass seed farming belt. Perennial ryegrass fields cover the valley floor, and during June–July peak season, pollen counts can reach extraordinary levels. Eugene has been described as one of the worst cities in the world for grass allergy sufferers.

Alder · Jan–MarGrass extreme · Jun–JulRagweed lighter than East

Portland Metro

Urban valley with heavy alder and oak

Portland experiences Oregon's full pollen sequence: heavy alder from January through March, followed by oak and birch in spring, then Willamette Valley grass drifting north June–July. The city's many street trees contribute to spring counts. Portland's mild, wet winters mean almost no true pollen break.

Alder · Jan–MarOak · Apr–MayGrass · Jun–Jul

Southern Oregon / Rogue Valley

Medford and a warmer, longer season

The Rogue Valley near Medford is shielded from Pacific moisture by the Siskiyou Mountains, creating a Mediterranean-like climate with warmer, drier summers. This pushes pollen onset earlier than the Willamette Valley. Oak is prominent in spring; ragweed is heavier here than in northern Oregon.

Oak · Mar–May (earlier)Grass · May–JulRagweed heavier south

Eastern Oregon

High desert and sagebrush season

Bend and eastern Oregon sit in the rain shadow of the Cascades, with much drier conditions and lower humidity. Overall pollen counts are lower than the Willamette Valley, but sagebrush and other weed pollens peak in fall. The dry air can actually make allergen particles travel farther and penetrate more deeply.

Juniper · Feb–AprGrass · May–Jun (lighter)Sagebrush · Aug–Oct

Each row shows a full year of pollen for one region — trees in blue, grasses in green, weeds in amber. Look for where all three rows go quiet at the same time — that's your window.

Oral Allergy Syndrome (also called pollen-food allergy syndrome) causes tingling or mild itching in the mouth when you eat certain raw foods during the relevant pollen season. The proteins in the food are similar enough to the pollen protein that your immune system cross-reacts. Cooking usually deactivates the offending protein, so the same food cooked may cause no reaction.

Alder & Birch pollen

Stone fruits, hazelnuts & apples

Apples, pears, peaches, cherries, plums, almonds, hazelnuts, carrots, celery, parsley

Peak risk January–April in Oregon — earlier and more intense than most US states. Hazelnut (filbert) is a particularly common cross-reactor given Oregon's large hazelnut crop.

Grass pollen

Tomatoes, potatoes & melons

Tomatoes, potatoes, kiwi, watermelon, cantaloupe, oranges (in some cases)

Peak risk May–July — especially severe in the Willamette Valley. Eugene grass counts during peak season are among the highest recorded anywhere in the world.

Ragweed & Mugwort

Melons, carrots & spices

Watermelon, cantaloupe, banana, carrot, celery, parsley, sunflower seeds, chamomile tea

Peak risk August–September. Oregon's ragweed is lighter than the East Coast, but mugwort is a notable additional weed allergen in the Pacific Northwest with its own cross-reactivity profile.

Not medical advice. If you suspect OAS, speak with an allergist — it can sometimes progress, and symptoms that extend beyond the mouth should be evaluated.