Decorah pollen forecast - today, tomorrow and the week ahead
Pollen Today
Today (20 September) pollen in Decorah is moderate; ragweed is moderate.
Pollen Tomorrow
Tomorrow (21 September 2026) levels are similar to today.
7-Day Trend
Over the next week grass, mugwort, and ragweed will increase.
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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) | Moderate | 44/100 |
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) | Moderate | 26/100 |
Local Environmental Conditions
The vegetation around Decorah, on the driftless-area bluffs above the Upper Iowa River, is dominated by oak-hickory forest and bur oak savanna, with riverside cottonwood adding further seasonal pollen exposure. Wind patterns across the area help determine how far pollen travels from these source plants. Residents who spend time outdoors around Decorah typically notice the shift as each season turns over.
Decorah's pollen season opens with elm and cottonwood from March with ash following close behind through April. Grass pollen rises through May and June, and ragweed and mugwort extend the season into September. The continental climate and surrounding farmland drive a well-defined spring tree peak and a strong late-summer ragweed season throughout the year.
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Frequently Asked Questions About Pollen in Iowa
Is pollen high in Decorah right now?
On 20 September 2026, overall pollen levels in Decorah are moderate. Ambrosia is the main contributor to airborne pollen
Will pollen levels change in Decorah tomorrow?
On 21 September 2026, pollen conditions in Decorah will be similar to today, with ambrosia at moderate levels
Is pollen expected to decrease in Decorah this week?
According to the five-day outlook, grass, ambrosia, and artemisia pollen levels will increase later in the week.
Which pollen types are currently active in Decorah?
On 20 September 2026, Ambrosia is the dominant pollen source in Decorah. grass and artemisia are not currently active.
When is pollen season in Decorah?
How often is the Decorah pollen forecast updated?
The Decorah pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in Decorah 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 Decorah 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 Decorah, 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).
