Worst air pollution Longueuil, today and tomorrow

On 9 August 2026, overall air quality in Longueuil is fair. AQI is the main air quality indicator at 37.5/100. Pollution peaks around 9:00 AM (O3: 37.5/100).

On 10 August 2026, air quality conditions in Longueuil will be similar to today, with AQI forecast at fair at 35.9/100. Pollution peaks around 11:00 AM (O3: 35.9/100).

The air over Longueuil varies through the year, influenced by its dense south-shore streets across the river from downtown Montréal. The warmest months typically see the poorest air quality, with heat and heavy traffic driving up smog levels on windless days, whereas fall and winter tend to bring cleaner, more variable conditions. Its distance from the island's dense core usually keeps conditions a little calmer than central Montréal.

It is forecasts derived by downscaling forecasts provided by EU’s Copernicus Atmosphere Monitoring Service (CAMS) by taking into account local conditions such as traffic patterns. CAMS bases its forecast on satellite measurements of particles and chemical compounds in the atmosphere. Airmine’s services were developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team.

Airmine’s forecast uses CAMS (Copernicus Atmosphere Monitoring Service) as its background atmospheric model. While CAMS includes wildfire emissions, these are derived from satellite observations and are not available in real time. During rapidly evolving wildfire events, there may therefore be a delay before increased emissions are incorporated into the model. As a result, the forecast may temporarily underestimate PM₂.₅ and other pollutants associated with wildfire smoke.

During rapidly evolving wildfire events, CAMS may lag by approximately 1–2 days before increased wildfire emissions are fully represented, which can lead to temporary underestimation of PM₂.₅ concentrations in Airmine’s forecast.