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Ichinomiya occupies a strategic position in the flat, fertile Nōbi Plain of central Japan, nestled between the Kiso River to the west and the larger Nagoya metropolitan area to the east. This location places it squarely within the industrial heartland of the Chūbu region, where urban sprawl from Nagoya merges with smaller manufacturing towns, creating a continuous urban-industrial corridor. The city's terrain is predominantly low-lying, with an average elevation of just 10 meters above sea level, which inhibits natural ventilation and allows pollutants to accumulate near ground level. Proximity to Ise Bay, approximately 30 kilometers to the south, introduces maritime influences that can moderate pollution but also contribute to humidity and fog formation, particularly in winter. Ichinomiya's urban character blends residential districts with light to medium industry, including textiles, machinery, and automotive parts production, typical of Aichi Prefecture's economic base. The surrounding landscape transitions from dense urbanization eastward toward Nagoya to more agricultural zones westward, where rice paddies and vegetable fields dominate, though these rural buffers are shrinking due to suburban expansion. This urban-rural gradient means pollution sources are diffuse, with vehicle emissions from major highways like the Meishin Expressway combining with industrial outputs and occasional agricultural burning. The city's position in a basin-like plain, flanked by low hills to the north and south, further traps airborne particulates, especially during stable weather conditions, making geographic context a key determinant of its air quality challenges.

In Ichinomiya, air quality follows a distinct seasonal rhythm shaped by Japan's temperate climate and regional meteorology. Spring, from March to May, sees moderate pollution levels as increasing daylight and occasional rain showers help disperse contaminants, though pollen from surrounding vegetation can aggravate respiratory issues. Summer, particularly June to August, brings the highest pollution risks due to intense sunlight driving ozone formation from vehicle and industrial emissions, compounded by high humidity that traps pollutants near the ground; sensitive groups should limit outdoor exertion on hot, stagnant afternoons. Autumn, spanning September to November, offers the cleanest air, with cooler temperatures, frequent winds from the northwest, and clearer skies that facilitate pollutant dispersion, making it the ideal season for outdoor activities. Winter, from December to February, presents challenges with temperature inversions common in the Nōbi Plain's low-lying areas, where cold air traps pollutants like PM2.5 from heating sources and traffic, often worsened by fog from Ise Bay; vulnerable individuals should monitor air quality indexes and reduce exposure on calm, cold mornings. Throughout the year, wind patterns play a crucial role, with sea breezes from the south providing temporary relief in summer, while winter northerlies can transport pollutants from Nagoya's industrial zones. There is no distinct monsoon, but seasonal shifts in pressure systems influence pollution peaks, with late summer ozone and winter particulate matter being the primary concerns for health guidance.