When is pollen worst in Dayton?

The late-summer ragweed run is the headline in Dayton: weed pollen peaks Aug–Nov, the longest and most punishing window of the year here. Tree pollen comes first (Feb–Apr) and grass bridges the gap (Apr–Sep), but it's the ragweed stretch that floors most sufferers. Currently, grass and ragweed pollen is what's driving counts this month.

What's in the air in Dayton right now?

In August, grass and ragweed pollen are in season in Dayton — the dominant allergens you're likely reacting to right now. A live count, when available, confirms the day's actual reading; this reflects the typical peak windows for Dayton's warm, humid subtropical Southeast climate.

Is tree or grass pollen higher in Dayton in spring?

In spring, tree pollen leads in Dayton — trees pollinate Feb–Apr, ahead of grass (Apr–Sep). 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 Dayton's pollen season distinctive?

Dayton sits in the warm, humid subtropical Southeast zone, which means an unusually long, overlapping season — the warm climate stretches grass across much of the year and pushes ragweed deep into autumn. That shapes when symptoms hit and which allergen to watch.

How do I reduce pollen exposure in Dayton?

Through Dayton's peak windows (tree Feb–Apr, grass Apr–Sep, ragweed Aug–Nov), 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.

What pollen index counts as high?

Pollen is reported on a categorical scale — None, Low, Moderate, High, and Very High. "High" and above means most allergy sufferers notice symptoms even with brief outdoor exposure, and sensitized people should limit time outside and pre-medicate. "Low" to "Moderate" usually only affects highly sensitive individuals.

What is the allergy forecast in Dayton today?

The allergy forecast is the airborne-pollen outlook that drives hay fever — exactly what this page tracks. Today's pollen level for Dayton is shown above, broken into the tree, grass, and ragweed pollen behind most seasonal allergies. When the reading is High or Very High, plan for symptoms and pre-medicate; the seasonal calendar below shows which allergen leads in each part of the year.

Dayton, Ohio Pollen Count & Allergy Forecast

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

Dayton, OH · Pollen season

In August, grass and ragweed pollen are in season in Dayton — the dominant allergens you're likely reacting to right now.

Based on the seasonal pollen calendar for this region.

Dayton on the WeatherStory Allergy Index

Dayton ranks #20 of 100 U.S. metros on the WeatherStory Allergy Index, with a modeled load index of 49 and a 304-day combined pollen season — its heaviest load is grass pollen, running 213 days.

#20of 100

Load index: 49
Combined season: 304 days
Heaviest load: Grass · 213 days

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

Typical now — Augustseasonal estimate, not a live reading

Grass pollen typically leads in Dayton this time of year, at an estimated High level. No live count is wired up; this reflects the seasonal calendar.

Pollen by type this season

TreeOut of seasonpeaks Feb–Apr
GrassIn seasonpeaks Apr–Sep
Weed / RagweedIn seasonpeaks Aug–Nov

What pollinates near Dayton

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

Trees

Oak Quercuspeaks March–April
Loblolly pine Pinus taedapeaks March–April
Pecan Carya illinoinensispeaks April–May
Sweetgum Liquidambar styracifluapeaks March–April
Mulberry Moruspeaks March–April
Elm Ulmuspeaks February–March

Grasses

Bermuda grass Cynodon dactylonpeaks May–September
Bahia grass Paspalum notatumpeaks May–September
Johnson grass Sorghum halepensepeaks June–August
Timothy Phleum pratensepeaks May–June

Weeds

Common ragweed Ambrosia artemisiifoliapeaks August–October
Giant ragweed Ambrosia trifidapeaks August–October
Pigweed Amaranthuspeaks August–September
English plantain Plantago lanceolatapeaks May–September

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

Dayton’s allergy year

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

JFMAMJJASOND

TreeFeb–May

GrassApr–Oct

RagweedAug–Nov

How Dayton compares to the U.S. average

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

Treeabout average

Grassabout average

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 Dayton’s pollen count works

The calendar above is tuned to Dayton’s warm, humid subtropical Southeast climate, not a national average: tree pollen runs from week 5 (early February) to week 18 (early May), grass from week 14 (early April) to week 40 (early October), and ragweed from week 31 (early August) to week 44 (early November) here — a 304-day combined pollen season. Those windows are why grass and ragweed pollen are in season in Dayton right now.

No live count is wired up for Dayton today, so the seasonal calendar above is your guide to which allergen is in season. Counts run highest on warm, dry, windy mornings and drop after rain, which washes pollen out of the air — reported on the None / Low / Moderate / High / Very High scale.

Frequently asked

When is pollen worst in Dayton?: The late-summer ragweed run is the headline in Dayton: weed pollen peaks Aug–Nov, the longest and most punishing window of the year here. Tree pollen comes first (Feb–Apr) and grass bridges the gap (Apr–Sep), but it's the ragweed stretch that floors most sufferers. Currently, grass and ragweed pollen is what's driving counts this month.
What's in the air in Dayton right now?: In August, grass and ragweed pollen are in season in Dayton — the dominant allergens you're likely reacting to right now. A live count, when available, confirms the day's actual reading; this reflects the typical peak windows for Dayton's warm, humid subtropical Southeast climate.
Is tree or grass pollen higher in Dayton in spring?: In spring, tree pollen leads in Dayton — trees pollinate Feb–Apr, ahead of grass (Apr–Sep). 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 Dayton's pollen season distinctive?: Dayton sits in the warm, humid subtropical Southeast zone, which means an unusually long, overlapping season — the warm climate stretches grass across much of the year and pushes ragweed deep into autumn. That shapes when symptoms hit and which allergen to watch.
How do I reduce pollen exposure in Dayton?: Through Dayton's peak windows (tree Feb–Apr, grass Apr–Sep, ragweed Aug–Nov), 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.
What pollen index counts as high?: Pollen is reported on a categorical scale — None, Low, Moderate, High, and Very High. "High" and above means most allergy sufferers notice symptoms even with brief outdoor exposure, and sensitized people should limit time outside and pre-medicate. "Low" to "Moderate" usually only affects highly sensitive individuals.
What is the allergy forecast in Dayton today?: The allergy forecast is the airborne-pollen outlook that drives hay fever — exactly what this page tracks. Today's pollen level for Dayton is shown above, broken into the tree, grass, and ragweed pollen behind most seasonal allergies. When the reading is High or Very High, plan for symptoms and pre-medicate; the seasonal calendar below shows which allergen leads in each part of the year.

Pollen & allergy guides

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

More for Dayton

See the full Dayton, OH weather forecast — hour-by-hour outlook, NOAA radar, satellite, and air quality.