East Gwillimbury pollen forecast — Harvest Hills neighborhood
Pollen Today
Today (20 September) pollen in Harvest Hills, East Gwillimbury is high; ragweed is high; grass is 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 | 48/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | Low | 24/100 |
| Ragweed (Ambrosia) | High | 57/100 |
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 | 4/100 | |
| Willow (Salicaceae) | None | 0/100 | — |
| Mugwort (Artemisia) | None | 0/100 | |
| Ragweed (Ambrosia) | Low | 13/100 |
Local Environmental Conditions
Nearby, in the surrounding area, the nearest stream or river hosts hazel and willow, two of the most allergenic early-season trees. A canopy of oak and birch, birch chief among them for allergenic potency here, just outside the immediate area. A stretch of mown parkland where turf and ornamental trees feed local grass and ragweed pollen, in the wider area.
The bank's hazel and willow kick off the pollen season ahead of the rest, peaking in late winter through March. The area's oak and birch trees pollinate through mid-to-late spring, climbing steadily through spring to a peak in April or May. Grass pollen takes over next, building to a peak around June, before ragweed takes over as the dominant allergen from mid-August through October.
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Frequently Asked Questions About Pollen in Ontario
Is pollen high in East Gwillimbury right now?
On 20 September 2026, overall pollen levels in East Gwillimbury are high. Ambrosia is the main contributor to airborne pollen, while grass and artemisia remain at lower levels
Will pollen levels change in East Gwillimbury tomorrow?
On 21 September 2026, pollen conditions in East Gwillimbury will be different from today, with ambrosia, grass continuing to decline
Is pollen expected to decrease in East Gwillimbury 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 East Gwillimbury?
On 20 September 2026, Ambrosia is the dominant pollen source in East Gwillimbury. grass and artemisia are also present but at lower levels.
When is pollen season in East Gwillimbury?
How often is the East Gwillimbury pollen forecast updated?
The East Gwillimbury pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in East Gwillimbury 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 East Gwillimbury 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 East Gwillimbury, 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. |
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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).
