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Fujisawa occupies a distinctive coastal position in Kanagawa Prefecture, Japan, situated on the western shore of Sagami Bay where the Shōnan coastal plain meets the foothills of the Tanzawa Mountains. This geography creates a unique urban-rural gradient, with the city's eastern waterfront transitioning westward through dense residential and commercial zones toward forested uplands. Fujisawa's elevation ranges from sea level along its 8.5-kilometer coastline to approximately 100 meters in its western reaches, creating subtle but meaningful microclimatic variations. The city forms part of the Greater Tokyo Metropolitan Area's southern corridor, positioned strategically between Yokohama's industrial belt to the north and more agricultural regions of western Kanagawa. Proximity to Sagami Bay significantly influences local air quality through sea breezes that typically disperse pollutants, though these effects can be moderated when westerly winds carry emissions from Tokyo-Yokohama industrial zones across the relatively flat Kanto Plain. The Tanzawa Mountains to the northwest occasionally create lee-side effects that trap pollutants under specific atmospheric conditions. Fujisawa's urban character blends traditional residential neighborhoods with modern commercial developments, lacking heavy industry within city limits but experiencing transportation-related pollution from major arteries like National Route 1 and the Tōkaidō Shinkansen line. The city's coastal location generally provides better air quality than inland urban centers, though regional pollution transport remains a concern during certain meteorological patterns.

Fujisawa's air quality follows distinct seasonal patterns shaped by its coastal location and regional meteorology. Spring (March-May) typically brings improving conditions as winter stagnation dissipates, though occasional kōsa (yellow dust) events from continental Asia can elevate particulate levels in April. The sea breeze becomes more consistent by late spring, providing natural ventilation. Summer (June-August) offers generally good air quality despite higher ozone formation potential, as prevailing southerly winds from the Pacific Ocean bring clean marine air across Sagami Bay. However, humid conditions combined with transported pollutants from the Kanto Plain can occasionally create hazy episodes. Autumn (September-November) represents the most favorable season, with stable atmospheric conditions, moderate temperatures, and consistent ventilation patterns minimizing pollution accumulation. Winter (December-February) presents the greatest challenges, as temperature inversions develop more frequently over the Kanto Plain, trapping pollutants near the surface. While Fujisawa's coastal position provides some mitigation, northerly winds can transport accumulated urban emissions from Tokyo-Yokohama southward. Sensitive groups should be particularly cautious during winter mornings when inversion layers are strongest and during spring kōsa events. The best months for outdoor activity are typically September through November, while January and February warrant increased awareness for those with respiratory conditions. Fog, though not a major hazard, can combine with pollutants during winter stagnation periods, reducing visibility and air quality temporarily.