Toronto Mold Forecast - Today, Tomorrow and the Week Ahead
Mold Today
Today (10 October) mold in Toronto is low; alternaria and cladosporium are low.
Mold Tomorrow
Tomorrow (11 October 2026) levels are similar to today.
7-Day Trend
Over the next week alternaria and cladosporium will decrease.
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Pollen & Air Quality
Mold for Neighborhoods
Pollen & AQ for Routes
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Local pollen and air quality forecasts, interactive pollen maps and route profiles
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Mold Risk
Today - 10 October
| Mold species | Level | Value |
|---|---|---|
| Alternaria | Low | 5/100 |
| Cladosporium | Low | 19/100 |
Tomorrow - 11 October
| Mold species | Level | Value | 7-Day Trend |
|---|---|---|---|
| Alternaria | Low | 5/100 | Steady |
| Cladosporium | Low | 18/100 | Steady |
Local Mold Conditions
Natural sources of organic matter for mold are relatively sparse around the heart of Toronto, apart from the green spaces among the buildings. Within the built-up area, mold finds food in compost heaps, mulched beds, grass clippings and leaves gathered along streets and gutters. The damp ground along a lake or pond nearby keeps leaf litter and plant debris moist for longer.
The mold season is led by Cladosporium, which thrives on garden waste and fallen leaves from May to October and peaks in July, at roughly 23°C. Alternaria needs more warmth and is most abundant in July. The cold months from December to March, with averages below 5°C, bring a long break from outdoor mold. Day to day, spores peak on dry, breezy afternoons after dew or light rain.
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Resource Hub
Mold forecast neighborhoods 80 neighborhoods
Sports venues in Toronto 9 sports venues
Popular Local Routes 6 routes
Local parkruns 6 parkruns
Frequently Asked Questions About Mold in Ontario
Why do I still have allergy symptoms after the pollen season?
Allergy symptoms after the main pollen season may be caused by mold spores. Outdoor mold levels can remain high into late summer and autumn, when pollen levels are already falling. Mold allergy can cause symptoms similar to pollen allergy, including sneezing, a runny or blocked nose, itchy eyes, coughing, and wheezing.
What are mold spores and why do they cause allergies?
Mold spores are tiny particles released by fungi into the air. When inhaled, they can trigger an allergic reaction in sensitive people. Common symptoms include sneezing, a runny or blocked nose, itchy or watery eyes, coughing, and wheezing.
When are mold spore levels highest?
Outdoor mold spore levels often increase during warm and humid conditions, particularly when there is plenty of decaying vegetation. Levels can vary considerably with weather, season, vegetation, and location, and some types of mold are more common during particular times of the year, e.g. in the Fall.
How can I reduce my exposure to mold spores?
If you are sensitive to mold, check local mold spore levels and forecasts before spending long periods outdoors. On high-risk days, reducing time around dense vegetation, compost, fallen leaves, and other sources of decaying plant material may help limit exposure.
Understanding the Scale
The 0–100 mold scores represent risk levels, not direct mold measurements. Higher scores indicate higher risk.
Mold
| 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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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.
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