London Mold Forecast
Mold Today
Today (16 September) mold in London is moderate; cladosporium is moderate; alternaria is low.
Mold Tomorrow
Tomorrow (17 September 2026) levels are similar to today.
7-Day Trend
Over the next week alternaria will increase; cladosporium will decrease.
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Mold Risk
Today - 16 September
| Mold species | Level | Value |
|---|---|---|
| Alternaria | Low | 10/100 |
| Cladosporium | Moderate | 33/100 |
Tomorrow - 17 September
| Mold species | Level | Value | 7-Day Trend |
|---|---|---|---|
| Alternaria | Low | 8/100 | Steady |
| Cladosporium | Moderate | 30/100 | Steady |
Local Mold Conditions
Mold needs both moisture and adequate warmth, and while London averages 72.2% soil moisture, its cool climate means temperature becomes a limiting factor for part of the year. Organic matter for mold to feed on is typically plentiful. Together, moisture, temperature, and organic supply favour strong growth for both Cladosporium and the more demanding Alternaria.
In London's cool climate, temperature is a real constraint on mold growth — the season opens when warmth arrives, regardless of moisture levels. Soil moisture reaches 86.0% in December and falls to its lowest in May, but temperature — not moisture — is what determines when mold is actually active here. Since both Cladosporium and Alternaria disperse spores in dry, windy conditions, airborne counts typically climb toward the drier, end of the warm season.
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Resource Hub
Pollen forecast neighborhoods 31 neighborhoods
Popular Local Routes 13 routes
Local parkruns 148 parkruns
Local events 7 events
Frequently Asked Questions About Mold in London, City of
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 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.
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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