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Saint-Augustin-de-Desmaures, nestled within the Quebec City metropolitan area, occupies a geographically significant position along the Saint Lawrence River. Its coordinates (46.7333, -71.4667) place it on a relatively flat alluvial plain, a legacy of glacial deposits and riverine activity. The city’s terrain is gently undulating, transitioning from the riverfront to slightly higher ground towards the interior, offering limited but noticeable elevation changes. This proximity to the Saint Lawrence, a major waterway and transportation corridor, influences local weather patterns and, consequently, air quality. The surrounding landscape is a blend of urban development, agricultural fields, and forested areas, creating a gradual urban–rural gradient. To the north and west lie predominantly agricultural zones, contributing occasional particulate matter from farming practices, while the broader Quebec City region hosts some light industrial activity, primarily focused on manufacturing and logistics, situated further upstream. The Laurentian Mountains, though distant, exert a regional influence on wind patterns and can occasionally trap pollutants under stable atmospheric conditions. The city’s location within the St. Lawrence Lowlands, a fertile and historically settled region, means it’s part of a densely populated corridor, impacting overall emissions. The river itself acts as a natural ventilation pathway, but can also concentrate pollutants under certain meteorological circumstances. The relatively flat topography limits dispersion, potentially leading to localized air quality challenges, particularly during periods of stagnant air.

Saint-Augustin-de-Desmaures experiences a distinct four-season climate, profoundly impacting its air quality profile. Winter (December-February) often presents the most challenging conditions. Cold temperatures and frequent temperature inversions, where a layer of warm air sits above colder air near the ground, trap pollutants close to the surface. This inversion layer inhibits vertical mixing, leading to a build-up of emissions from residential heating (primarily natural gas and heating oil) and vehicle traffic. Fog, common during these months, further exacerbates the problem by reducing visibility and trapping particulate matter. Spring (March-May) brings a gradual improvement as temperatures rise and wind speeds increase, dispersing pollutants. However, agricultural activities, such as tilling and fertilizer application, can contribute to localized dust and ammonia emissions. Summer (June-August) generally offers the best air quality, with consistent winds and higher mixing heights. However, occasional heatwaves can lead to stagnant air conditions and increased ozone formation, a secondary pollutant. Fall (September-November) sees a transition period, with cooler temperatures and changing wind patterns. Leaf burning, though regulated, can contribute to localized smoke events. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should be particularly cautious during winter months, limiting outdoor exertion on days with poor visibility. During the spring, awareness of agricultural emissions is advised. Summer heatwaves warrant monitoring for ozone alerts, and fall requires vigilance regarding potential smoke events.