When is pollen worst in Keystone?

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

What's in the air in Keystone right now?

Right now tree pollen leads in Keystone at a Moderate (3/5) level. The species actually in the air today: Birch, Pine, Oak, and Grasses. On a quiet live day, Keystone's seasonal calendar fills in what's typically airborne this time of year.

Is tree or grass pollen higher in Keystone in spring?

In spring, tree pollen leads in Keystone — trees pollinate Mar–May, ahead of grass (May–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 Keystone's pollen season distinctive?

Keystone sits in the continental Plains zone, which means the country's worst ragweed — the continental Plains run a long, severe late-summer-into-fall weed season on top of the usual tree and grass peaks. That shapes when symptoms hit and which allergen to watch.

How do I reduce pollen exposure in Keystone?

Through Keystone's peak windows (tree Mar–May, grass May–Jul, 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.

Keystone, South Dakota Pollen Count

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

Keystone, SD · Pollen count right now

Tree pollen is Moderate in Keystone today

Tree: Moderate 3/5Grass: Low 2/5Tomorrow: High

Today’s pollen by type

TreeModerate3/5
GrassLow2/5
Weed / RagweedOut of season

Active now: Birch, Pine, Oak, Grasses.

Keystone pollen calendar

Typical peak months for each pollen type in this climate region. The highlighted column is the current month.

JFMAMJJASOND

TreeMar–May

GrassMay–Jul

WeedAug–Nov

Allergy relief

Zyrtec 24-Hour Allergy Relief (Cetirizine 10 mg)
A once-daily, non-drowsy oral antihistamine. Start it a couple of weeks before your worst pollen season for the best symptom control.
View on Amazon →
NeilMed Sinus Rinse Kit (Saline Nasal Irrigation)
A saline rinse physically flushes pollen out of the nasal passages. Use it after time outdoors during peak season to cut the allergen load before symptoms build.
View on Amazon →

Weather Story is a participant in the Amazon Associates program. As an Amazon Associate we earn from qualifying purchases — at no extra cost to you. Product picks are editorial; the links above are affiliate links.

How Keystone’s pollen count works

The calendar above is tuned to Keystone’s continental Plains climate, not a national average: tree pollen peaks Mar–May, grass May–Jul, and ragweed Aug–Nov here. Those windows are why grass pollen is the one in season in Keystone right now.

Right now tree pollen leads in Keystone at a Moderate (3/5) level. The species actually in the air today: Birch, Pine, Oak, and Grasses. 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 Keystone?: The late-summer ragweed run is the headline in Keystone: weed pollen peaks Aug–Nov, the longest and most punishing window of the year here. Tree pollen comes first (Mar–May) and grass bridges the gap (May–Jul), but it's the ragweed stretch that floors most sufferers. Currently, grass pollen is what's driving counts this month.
What's in the air in Keystone right now?: Right now tree pollen leads in Keystone at a Moderate (3/5) level. The species actually in the air today: Birch, Pine, Oak, and Grasses. On a quiet live day, Keystone's seasonal calendar fills in what's typically airborne this time of year.
Is tree or grass pollen higher in Keystone in spring?: In spring, tree pollen leads in Keystone — trees pollinate Mar–May, ahead of grass (May–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 Keystone's pollen season distinctive?: Keystone sits in the continental Plains zone, which means the country's worst ragweed — the continental Plains run a long, severe late-summer-into-fall weed season on top of the usual tree and grass peaks. That shapes when symptoms hit and which allergen to watch.
How do I reduce pollen exposure in Keystone?: Through Keystone's peak windows (tree Mar–May, grass May–Jul, 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.

More for Keystone

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