St. Clair pollen forecast - today, tomorrow and the week ahead
Pollen Today
Today (20 September) pollen in St. Clair is moderate; grass and ragweed are moderate; mugwort is low.
Pollen Tomorrow
Tomorrow (21 September 2026) grass declining, ragweed declining, mugwort no longer expected.
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) | Moderate | 33/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | Low | 11/100 |
| 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) | Low | 8/100 | |
| Willow (Salicaceae) | None | 0/100 | — |
| Mugwort (Artemisia) | None | 0/100 | |
| Ragweed (Ambrosia) | Low | 18/100 |
Local Environmental Conditions
Along the damp banks, hazel and willow release some of the year's first tree pollen, just outside the immediate area. Located not far from here, this area has a park whose lawns and ornamental trees quietly add to grass and ragweed pollen levels. Local wind exposure and land use can shift the exact mix slightly from block to block.
The bank's hazel and willow kick off the pollen season ahead of the rest, getting an early start, typically cresting between February and March. Grass pollen becomes the dominant allergen through late spring, peaking in June, and then ragweed picks up the slack, running from mid-August through October. Local weather swings can shift these windows slightly, but the overall order tends to hold.
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Pollen forecast neighborhoods 2 neighborhoods
Frequently Asked Questions About Pollen in Pennsylvania
Is pollen high in St. Clair right now?
On 20 September 2026, overall pollen levels in St. Clair are moderate. Ambrosia is the main contributor to airborne pollen, while grass and artemisia remain at lower levels
Will pollen levels change in St. Clair tomorrow?
On 21 September 2026, pollen conditions in St. Clair will be different from today, with ambrosia, grass continuing to decline
Is pollen expected to decrease in St. Clair 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. Clair?
On 20 September 2026, Ambrosia is the dominant pollen source in St. Clair. grass and artemisia are also present but at lower levels.
When is pollen season in St. Clair?
How often is the St. Clair pollen forecast updated?
The St. Clair pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in St. Clair 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. Clair 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. Clair, 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).
