St. Charles pollen forecast - today, tomorrow and the week ahead
Pollen Today
Today (20 September) pollen in St. Charles is moderate; ragweed is moderate; grass is low.
Pollen Tomorrow
Tomorrow (21 September 2026) ragweed declining, grass no longer expected.
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) | Low | 3/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | None | 0/100 |
| Ragweed (Ambrosia) | Moderate | 26/100 |
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 | 12/100 |
Local Environmental Conditions
In St. Charles, hazel and willow grow near the nearby bank, known for pollen that travels far. St. Charles has a nearby green space's lawns and planted trees add a small share of grass and ragweed pollen. Small elevation or soil differences can shift these figures a bit.
Waterside hazel and willow bloom first, cresting most years in February or March. Grass pollen rises steadily, cresting in June, and ragweed follows from mid-August into October.
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Resource Hub
Sports venues in St. Charles 2 sports venues
Frequently Asked Questions About Pollen in Illinois
Is pollen high in St. Charles right now?
On 20 September 2026, overall pollen levels in St. Charles are moderate. Ambrosia is the main contributor to airborne pollen, while grass remain at lower levels
Will pollen levels change in St. Charles tomorrow?
On 21 September 2026, pollen conditions in St. Charles will be different from today, with ambrosia continuing to decline
Is pollen expected to decrease in St. Charles 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 St. Charles?
On 20 September 2026, Ambrosia is the dominant pollen source in St. Charles. grass are also present but at lower levels. artemisia are not currently active.
When is pollen season in St. Charles?
How often is the St. Charles pollen forecast updated?
The St. Charles pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in St. Charles 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 St. Charles 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 St. Charles, 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).
