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Yokkaichi occupies a strategic position along Ise Bay in central Japan's Mie Prefecture, situated on the coastal plain of the Kansai region where the Suzuka Mountains rise sharply to the west. This geography creates a distinct urban character shaped by its industrial heritage and proximity to major transportation corridors. The city lies at approximately sea level with minimal elevation variation, nestled between the bay to the east and the mountainous terrain to the west, creating a natural amphitheater effect that can trap pollutants. Yokkaichi forms part of the Keihanshin industrial belt extending from Osaka to Nagoya, with its port facilities handling petroleum, chemicals, and manufactured goods. The surrounding landscape transitions from dense urban development in the coastal zone to agricultural areas producing tea and rice in the foothills, creating an urban–rural gradient that influences pollution dispersion. Ise Bay's waters moderate temperatures but also contribute to humidity and occasional sea fog. The city's location at the crossroads of major air currents—with prevailing westerlies from the Asian continent and seasonal monsoonal flows—means it receives both locally generated emissions from its industrial complexes and transported pollutants from broader regional sources. The combination of industrial concentration, topographic containment, and maritime influences creates complex air quality dynamics where sea breezes can alternately disperse or recirculate pollutants depending on atmospheric conditions.

Yokkaichi's air quality follows distinct seasonal patterns shaped by Japan's temperate climate and regional meteorological systems. In winter (December-February), cold air from the Asian continent combines with frequent temperature inversions in the Suzuka basin, trapping pollutants near the surface and creating the year's worst air quality episodes. Sensitive groups should limit prolonged outdoor exposure during calm winter mornings when industrial emissions accumulate. Spring (March-May) brings improving conditions as increasing solar radiation breaks up inversions and southerly winds begin dispersing pollutants, though occasional yellow dust events from continental Asia can temporarily degrade air quality in April. Summer (June-August) offers generally favorable conditions despite high humidity, as the East Asian monsoon brings consistent southeasterly winds from the Pacific that effectively ventilate the basin, though intense heat can accelerate ozone formation on stagnant days. Autumn (September-November) typically provides the cleanest air as typhoon remnants clear the atmosphere and stable high-pressure systems dominate, making October and November ideal months for outdoor activities. Throughout the year, sea breezes from Ise Bay provide daily ventilation during afternoon hours, while nighttime land breezes can occasionally recirculate pollutants back toward the city. Residents with respiratory conditions should monitor daily forecasts particularly during winter inversion periods and summer ozone alerts, adjusting outdoor exercise to midday when mixing heights are highest.