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Fuchū, situated in western Tokyo Metropolis, occupies a distinctive position within Japan's Kanto Plain, approximately 20 kilometers west of central Tokyo's urban core. This city of 260,508 residents lies at coordinates 35.6689°N, 139.4776°E, with an average elevation of 60 meters above sea level, creating subtle topographical variations that influence local air circulation patterns. Geographically, Fuchū represents a transitional urban-rural gradient between Tokyo's dense central wards and the more agricultural western regions of the prefecture, featuring both residential neighborhoods and preserved green spaces like Fuchū-no-Mori Park. The city's location places it within Tokyo's broader metropolitan airshed, where regional pollution transport significantly impacts local air quality. Proximity to the Tama River system provides some natural ventilation corridors, while its position downwind from industrial zones in Kawasaki and Yokohama to the southeast means it receives transported pollutants under prevailing wind conditions. The surrounding landscape of gently rolling plains offers limited topographical barriers to air movement, allowing both clean air from western mountainous regions and polluted air from eastern industrial areas to flow through depending on seasonal wind patterns. Fuchū's urban character as a commuter suburb with extensive transportation infrastructure contributes local emissions from vehicular traffic along major routes like National Route 20 and the Chūō Expressway, while its distance from central Tokyo's densest emission sources provides some mitigation compared to inner-city areas.

Fuchū's air quality follows distinct seasonal patterns shaped by Tokyo's temperate climate with four clear seasons. During winter (December-February), cold, stable atmospheric conditions frequently create temperature inversions that trap pollutants near the surface, particularly during calm mornings when heating emissions peak. This season presents the highest pollution risks, with January typically showing the poorest air quality due to increased residential heating and limited atmospheric mixing. Sensitive groups should limit prolonged outdoor exertion during winter mornings when inversion layers are strongest. Spring (March-May) brings gradual improvement as increasing solar radiation breaks up inversion layers and stronger winds provide better dispersion, though pollen from surrounding vegetation can create additional respiratory challenges. Summer (June-August) features the cleanest air despite high temperatures, as southerly monsoon winds from the Pacific Ocean bring fresh marine air while convective mixing efficiently disperses pollutants, though occasional stagnant periods during the rainy season (tsuyu) in June can cause temporary accumulation. Autumn (September-November) begins with relatively good air quality that gradually deteriorates as temperatures drop and atmospheric stability increases, with November often showing a noticeable decline as heating season commences. The seasonal transition months of April and October generally offer the most favorable conditions for outdoor activities, while January requires the most caution for those with respiratory or cardiovascular conditions.