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Niles, Illinois, a suburb of Chicago, occupies a relatively flat portion of the Chicago Plain, a glacial landform characterized by morainal deposits. Its coordinates (42.0278, -87.8099) place it within Cook County, a densely populated region. The terrain is gently rolling, a legacy of past glacial activity, with elevations generally between 600 and 700 feet above sea level. The North Branch of the Chicago River flows nearby, influencing local humidity and potentially trapping pollutants during temperature inversions. Niles is situated within the broader Chicago metropolitan area, a major industrial and transportation hub. Historically, the region supported significant manufacturing, and while that has diversified, residual industrial activity and heavy traffic contribute to air quality concerns. The urban-rural gradient is pronounced; moving north and west from Niles quickly transitions into agricultural land, while the city itself is heavily developed with residential, commercial, and light industrial areas. Proximity to O'Hare International Airport also introduces a source of particulate matter. The prevailing winds, generally from the southwest, can transport pollutants from the city of Chicago and surrounding industrial areas directly over Niles, impacting local air quality. This geographic positioning makes Niles susceptible to both locally generated and regionally transported pollution.

Niles experiences a four-season climate, with distinct impacts on air quality. Spring (March-May) often sees moderate pollution levels as temperatures rise and vehicle use increases after winter, coupled with agricultural practices generating dust. Summer (June-August) typically presents the best air quality, aided by prevailing winds dispersing pollutants and rainfall cleansing the atmosphere, though ozone formation can be a concern on hot, stagnant days. August is generally the most favourable month for outdoor activity. Autumn (September-November) brings a return to increased pollution as temperatures drop, leading to temperature inversions that trap pollutants near the ground. Wood burning for heating also contributes to particulate matter. November can be particularly challenging. Winter (December-February) is often the worst period for air quality, with cold temperatures promoting increased use of heating fuels, and frequent temperature inversions exacerbating pollution. Snowfall can temporarily improve conditions, but also disrupts traffic, leading to localised increases in vehicle emissions. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor activity during winter and autumn months. Fog, common in the colder months, can also trap pollutants, reducing visibility and worsening air quality.