When is pollen worst in Seattle?

Seattle runs the classic three-wave calendar: tree pollen Feb–May, grass Apr–Jul, then ragweed Aug–Oct. The two worst stretches are the spring tree peak and the late-summer ragweed peak. Currently, ragweed pollen is in season.

What's in the air in Seattle right now?

In September, ragweed pollen is in season in Seattle, peaking Aug–Oct. On Seattle's mild, wet Pacific Northwest calendar the typical September level is Moderate, led by ragweed pollen — a seasonal estimate, not a live count.

Is tree or grass pollen higher in Seattle in spring?

In spring, tree pollen leads in Seattle — trees pollinate Feb–May, ahead of grass (Apr–Jul). The handoff is the tail of the tree window: tree counts taper as grass climbs, so an early-spring flare is more likely tree pollen and a late-spring one more likely grass.

What makes Seattle's pollen season distinctive?

Seattle sits in the mild, wet Pacific Northwest zone, which means a mild, wet pattern in which a long grass season is usually the bigger problem than the early tree burst, and ragweed stays light. That shapes when symptoms hit and which allergen to watch.

How do I reduce pollen exposure in Seattle?

Through Seattle's peak windows (tree Feb–May, grass Apr–Jul, ragweed Aug–Oct), keep windows shut and run AC on recirculate; counts run highest on dry, warm, windy mornings, so push outdoor activity to late afternoon or just after rain, which clears pollen from the air. A HEPA purifier indoors, a saline rinse after being outside, showering before bed, and starting antihistamines a week or two before your worst local window all measurably cut symptoms.

When does the next pollen season start in Seattle?

Tree pollen is next in Seattle: it opens around week 5 (early February), peaks around week 15, and runs about 122 days.

What is the allergy forecast in Seattle today?

With no live reading for Seattle today, its allergy forecast is the seasonal estimate above: a typical September level of Moderate, led by ragweed pollen.

Seattle, Washington Pollen Count & Allergy Forecast

Seattle pollen count and allergy forecast — tree, grass, and ragweed seasons and what’s pollinating now

Seattle, WA · Pollen season

In September, ragweed pollen is in season in Seattle, peaking Aug–Oct.

Based on the seasonal pollen calendar for this region.

Seattle on the WeatherStory Allergy Index

Seattle ranks #53 of 100 U.S. metros on the WeatherStory Allergy Index, with a modeled load index of 30 and a 274-day combined pollen season — its heaviest load is tree pollen, running 122 days.

#53of 100

Load index: 30
Combined season: 274 days
Heaviest load: Tree · 122 days

See the full 100 worst U.S. cities for pollen — a modeled seasonal load ranking (see methodology).

Typical now — Septemberseasonal estimate, not a live reading

Ragweed pollen typically leads in Seattle in September, at an estimated Moderate level.

Pollen by type this season

TreeOut of seasonpeaks Feb–May
GrassOut of seasonpeaks Apr–Jul
Weed / RagweedIn seasonpeaks Aug–Oct

What pollinates near Seattle

The tree, grass, and weed species that drive Seattle’s pollen seasons, with each plant’s typical peak.

Trees

Alder Alnuspeaks February–March
Birch Betulapeaks March–April
Western red cedar Thuja plicatapeaks March–April
Douglas fir Pseudotsuga menziesiipeaks April–May
Oak Quercuspeaks April–May

Grasses

Perennial ryegrass Lolium perennepeaks May–July
Orchard grass Dactylis glomeratapeaks May–July
Timothy Phleum pratensepeaks June–July
Kentucky bluegrass Poa pratensispeaks May–June

Weeds

Common ragweed Ambrosia artemisiifoliapeaks August–September
Plantain Plantagopeaks June–August
Lamb's quarters Chenopodium albumpeaks July–September
Sheep sorrel Rumex acetosellapeaks May–July

Species are the region’s common wind-pollinated plants; peak months are a seasonal estimate, not a measured count — see methodology.

Seattle’s allergy year

Typical month-by-month pollen intensity for Seattle, tuned to its latitude and climate region — darker means higher typical counts. The highlighted column is the current month.

JFMAMJJASOND

TreeFeb–May

GrassApr–Jul

RagweedAug–Oct

How Seattle compares to the U.S. average

Each colored bar is Seattle’s typical season against the national-average window (grey). The offset is the per-city timing shift.

Tree~4 wks earlier

Grass~4 wks earlier

Ragweedabout average

“U.S. average” is the textbook tree Mar–May, grass May–Jul, ragweed Aug–Oct calendar. The shift is a phenology estimate (Hopkins’ bioclimatic law), not a measured count — see methodology.

How Seattle’s pollen count works

The calendar above is tuned to Seattle’s mild, wet Pacific Northwest climate, not a national average: tree pollen runs from week 5 (early February) to week 22 (late May), grass from week 14 (early April) to week 30 (late July), and ragweed from week 31 (early August) to week 43 (late October) here — a 274-day combined pollen season. Those windows are why ragweed pollen is the one in season in Seattle right now.

No live count is wired up for Seattle today, so the seasonal calendar above is your guide to which allergen is in season.

For the science behind Seattle’s pollen seasons — how counts are measured, when each type peaks, and what the numbers mean — see the pollen count scale and the other pollen & allergy guides.

Frequently asked

When is pollen worst in Seattle?: Seattle runs the classic three-wave calendar: tree pollen Feb–May, grass Apr–Jul, then ragweed Aug–Oct. The two worst stretches are the spring tree peak and the late-summer ragweed peak. Currently, ragweed pollen is in season.
What's in the air in Seattle right now?: In September, ragweed pollen is in season in Seattle, peaking Aug–Oct. On Seattle's mild, wet Pacific Northwest calendar the typical September level is Moderate, led by ragweed pollen — a seasonal estimate, not a live count.
Is tree or grass pollen higher in Seattle in spring?: In spring, tree pollen leads in Seattle — trees pollinate Feb–May, ahead of grass (Apr–Jul). The handoff is the tail of the tree window: tree counts taper as grass climbs, so an early-spring flare is more likely tree pollen and a late-spring one more likely grass.
What makes Seattle's pollen season distinctive?: Seattle sits in the mild, wet Pacific Northwest zone, which means a mild, wet pattern in which a long grass season is usually the bigger problem than the early tree burst, and ragweed stays light. That shapes when symptoms hit and which allergen to watch.
How do I reduce pollen exposure in Seattle?: Through Seattle's peak windows (tree Feb–May, grass Apr–Jul, ragweed Aug–Oct), keep windows shut and run AC on recirculate; counts run highest on dry, warm, windy mornings, so push outdoor activity to late afternoon or just after rain, which clears pollen from the air. A HEPA purifier indoors, a saline rinse after being outside, showering before bed, and starting antihistamines a week or two before your worst local window all measurably cut symptoms.
When does the next pollen season start in Seattle?: Tree pollen is next in Seattle: it opens around week 5 (early February), peaks around week 15, and runs about 122 days.
What is the allergy forecast in Seattle today?: With no live reading for Seattle today, its allergy forecast is the seasonal estimate above: a typical September level of Moderate, led by ragweed pollen.