Keystone pollen forecast - today, tomorrow and the week ahead
Pollen Today
Today (20 September) pollen in Keystone is none
Pollen Tomorrow
Tomorrow (21 September 2026) ragweed at low levels.
7-Day Trend
Over the next week grass, mugwort, and ragweed will increase.
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Air Quality
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Local pollen and air quality forecasts, interactive pollen maps and route profiles
Features and forecast availability vary by region.
Pollen Risk
Today - 20 September
| Pollen species | Level | Value |
|---|---|---|
| Alder (Alnus) | None | 0/100 |
| Birch (Betula) | None | 0/100 |
| Hazel (Corylus) | None | 0/100 |
| Cypress (Cupressaceae) | None | 0/100 |
| Grass (Poaceae) | None | 0/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | None | 0/100 |
| Ragweed (Ambrosia) | None | 0/100 |
Tomorrow - 21 September
| Pollen species | Level | Value | 7-Day Trend |
|---|---|---|---|
| Alder (Alnus) | None | 0/100 | — |
| Birch (Betula) | None | 0/100 | — |
| Hazel (Corylus) | None | 0/100 | — |
| Cypress (Cupressaceae) | None | 0/100 | — |
| Grass (Poaceae) | None | 0/100 | |
| Willow (Salicaceae) | None | 0/100 | — |
| Mugwort (Artemisia) | None | 0/100 | |
| Ragweed (Ambrosia) | Low | 9/100 |
Local Environmental Conditions
Crazy Horse Memorial is a black Hills with ponderosa pine forest and granite formations. Pine pollen peaks in late May and June. The Hills' isolated forest produces a contained pollen season before summer heat sets in.
Crazy Horse Memorial tracks Keystone's broader pollen pattern, with elm and cottonwood appearing from March with ash taking the lead through April. A grass pollen peak follows through May and June; a strong ragweed peak follows in late summer into September. Wide-open plains terrain lets pollen travel long distances on the prevailing wind throughout the year.
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Frequently Asked Questions About Pollen in South Dakota
Is pollen high in Keystone right now?
Currently, there is no significant pollen in Keystone.
Will pollen levels change in Keystone tomorrow?
On 21 September 2026, pollen conditions in Keystone will be different from today, with ambrosia at low levels
Is pollen expected to decrease in Keystone this week?
According to the five-day outlook, ambrosia, artemisia, and grass pollen levels will increase later in the week.
Which pollen types are currently active in Keystone?
On 20 September 2026, there are no significant pollen types in Keystone.
When is pollen season in Keystone?
How often is the Keystone pollen forecast updated?
The Keystone pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in Keystone come from nearby or far away?
Studies show that most pollen exposure (often 70–90%) comes from nearby sources, such as local trees and vegetation. A good pollen forecast therefore depends on accurately representing local vegetation. Pollen can travel long distances, but this usually matters only early in the season or during specific wind events.
Are pollen levels in Keystone based on measurements or forecasts?
Pollen data is often misunderstood. Most "pollen levels" are not real-time measurements, but forecasts.
Direct pollen measurements are typically delayed by 1-2 days because they require manual analysis. To show current conditions in Keystone, modern forecasts combine recent measurements, weather data, and information about local vegetation.
This allows us to estimate pollen levels for today and the coming days, not just report the past.
Airmine’s atmospheric monitoring platform was developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team, using satellite and Earth observation technologies to improve emissions monitoring.
Understanding the Scale
The 0–100 scores represent risk levels, not direct measurements of pollen or air pollutant concentrations. Higher scores indicate higher risk. Pollen and air quality use different thresholds.
Pollen
| None | 0 | No or negligible risk of exposure. Pollen/mold exposure is expected to be minimal. |
| Low | 0-25 | Low risk of exposure. Small amounts of pollen or mold spores may be present. |
| Moderate | 25-50 | Moderate risk of exposure. Pollen/mold exposure is expected to be noticeable. |
| High | 50-75 | High risk of exposure. Elevated pollen/mold exposure is expected. |
| Very High | 75-100 | Very high risk of exposure. Pollen/mold exposure is expected to be at or near its highest levels. |
Get More in the Airmine Pollen app
Get 15-day pollen forecasts with morning, afternoon and evening detail, plus 5-day air quality forecasts. Explore interactive pollen risk maps, estimated pollen season start, route profiles and a symptoms diary.
Features and forecast availability vary by region. Currently covering Europe, the contiguous US, southern Canada, South Africa, Australia, Indonesia (Java & Bali), Brazil, Paraguay, Uruguay and the Buenos Aires area.
Developed with support from the European Space Agency (ESA) Business Applications and Space Solutions (BASS).
