When is pollen worst in Santa Rosa?

Tree pollen jumps the gun in Santa Rosa, opening as early as Feb–May while colder regions are still dormant. Grass follows Apr–Jul and ragweed closes the year Aug–Oct. The early tree start is the trap — symptoms can begin before you expect them. Currently, ragweed pollen is in season.

What's in the air in Santa Rosa right now?

In September, ragweed pollen is in season in Santa Rosa, peaking Aug–Oct. On Santa Rosa's mild Mediterranean California 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 Santa Rosa in spring?

In spring, tree pollen leads in Santa Rosa — 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 Santa Rosa's pollen season distinctive?

Santa Rosa sits in the mild Mediterranean California zone, which means an early start — mild winters pull tree pollen forward into late winter, ahead of a spring grass peak and a relatively contained ragweed fall. That shapes when symptoms hit and which allergen to watch.

How do I reduce pollen exposure in Santa Rosa?

Through Santa Rosa'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 Santa Rosa?

Tree pollen is next in Santa Rosa: it opens around week 5 (early February), peaks around week 11, and runs about 122 days.

What is the allergy forecast in Santa Rosa today?

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

Santa Rosa, California Pollen Count & Allergy Forecast

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

Santa Rosa, CA · Pollen season

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

Based on the seasonal pollen calendar for this region.

Santa Rosa on the WeatherStory Allergy Index

Santa Rosa isn't one of the 100 metros on the WeatherStory Allergy Index, but the nearest ranked metro — San Francisco, CA, about 50 miles away — sits at #42 with a 274-day combined pollen season.

#42of 100nearest ranked metro

Load index: 34
Combined season: 274 days
Heaviest load: Tree · 122 days
Nearest ranked metro: San Francisco, CA · ~50 mi

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 Santa Rosa 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 Santa Rosa

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

Trees

Oak Quercuspeaks March–April
Olive Olea europaeapeaks April–May
Coast live oak Quercus agrifoliapeaks March–April
Walnut Juglanspeaks April–May
Ash Fraxinuspeaks February–March
Mulberry Moruspeaks February–March

Grasses

Bermuda grass Cynodon dactylonpeaks April–June
Wild oat Avena fatuapeaks April–May
Perennial ryegrass Lolium perennepeaks April–June
Bromegrass Bromuspeaks April–May

Weeds

Common ragweed Ambrosia artemisiifoliapeaks August–September
Russian thistle Salsola traguspeaks July–September
Pigweed Amaranthuspeaks August–September
Sagebrush Artemisiapeaks August–September

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

Santa Rosa’s allergy year

Typical month-by-month pollen intensity for Santa Rosa, 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 Santa Rosa compares to the U.S. average

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

Tree~6 wks earlier

Grass~6 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 Santa Rosa’s pollen count works

The calendar above is tuned to Santa Rosa’s mild Mediterranean California 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 Santa Rosa right now.

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

For the science behind Santa Rosa’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 Santa Rosa?: Tree pollen jumps the gun in Santa Rosa, opening as early as Feb–May while colder regions are still dormant. Grass follows Apr–Jul and ragweed closes the year Aug–Oct. The early tree start is the trap — symptoms can begin before you expect them. Currently, ragweed pollen is in season.
What's in the air in Santa Rosa right now?: In September, ragweed pollen is in season in Santa Rosa, peaking Aug–Oct. On Santa Rosa's mild Mediterranean California 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 Santa Rosa in spring?: In spring, tree pollen leads in Santa Rosa — 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 Santa Rosa's pollen season distinctive?: Santa Rosa sits in the mild Mediterranean California zone, which means an early start — mild winters pull tree pollen forward into late winter, ahead of a spring grass peak and a relatively contained ragweed fall. That shapes when symptoms hit and which allergen to watch.
How do I reduce pollen exposure in Santa Rosa?: Through Santa Rosa'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 Santa Rosa?: Tree pollen is next in Santa Rosa: it opens around week 5 (early February), peaks around week 11, and runs about 122 days.
What is the allergy forecast in Santa Rosa today?: With no live reading for Santa Rosa today, its allergy forecast is the seasonal estimate above: a typical September level of Moderate, led by ragweed pollen.