Alton pollen forecast - today, tomorrow and the week ahead
Pollen Today
Today (20 September) pollen in Alton is moderate; ragweed is moderate; grass is low.
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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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) | Low | 22/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | None | 0/100 |
| Ragweed (Ambrosia) | Moderate | 47/100 |
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) | Low | 12/100 | |
| Willow (Salicaceae) | None | 0/100 | — |
| Mugwort (Artemisia) | None | 0/100 | |
| Ragweed (Ambrosia) | Moderate | 37/100 |
Local Environmental Conditions
Alton's Mississippi River bluff setting features oak, hickory, and sycamore as the main tree pollen sources, with exposure varying between the wooded bluff residential areas and the more built-up river bottom commercial corridors. The dramatic limestone bluffs concentrate pollen under certain wind conditions, while the Mississippi River floodplain below creates a distinct pollen zone from the upland residential areas above.
Alton's Mississippi River setting in southwestern Illinois produces a season opening in late February with elm and maple before oak peaks through April. Grass from surrounding Illinois farmland peaks through June and July before mugwort and nettle extend exposure into September. The Mississippi River bluffs channel airflows, while the warm Midwest climate advances the season slightly compared to more northern Illinois cities.
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Resource Hub
Sports venues in Alton 1 sports venue
Frequently Asked Questions About Pollen in Illinois
Is pollen high in Alton right now?
On 20 September 2026, overall pollen levels in Alton are moderate. Ambrosia is the main contributor to airborne pollen, while grass remain at lower levels
Will pollen levels change in Alton tomorrow?
On 21 September 2026, pollen conditions in Alton will be similar to today, with ambrosia at moderate levels, grass at low levels
Is pollen expected to decrease in Alton 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 Alton?
On 20 September 2026, Ambrosia is the dominant pollen source in Alton. grass are also present but at lower levels. artemisia are not currently active.
When is pollen season in Alton?
How often is the Alton pollen forecast updated?
The Alton pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in Alton 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 Alton 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 Alton, 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).
