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Kasamatsuchō is nestled within the fertile Nōbi Plain of Gifu Prefecture, serving as a transitional zone between the bustling urban core of Gifu City and the serene rural hinterlands. The town's geography is defined by its proximity to the Kiso and Nagara rivers, which provide essential drainage and moisture but also influence local microclimates. To the north and west, the imposing peaks of the Japanese Alps create a natural barrier, contributing to a basin-like topography that significantly affects atmospheric circulation. This low-lying terrain often traps stagnant air masses, particularly during periods of high pressure, which can lead to the accumulation of particulate matter. The urban character of Kasamatsuchō is a tapestry of traditional residential clusters, scattered agricultural plots, and light industrial zones, creating a complex urban–rural gradient. This mixture means that while the town enjoys the freshness of surrounding greenery, it is also susceptible to pollutants drifting from the industrial belts of the wider Nōbi Plain. The elevation is relatively low, ensuring a humid subtropical climate where moisture often clings to the valley floor. This humidity can exacerbate the effects of smog by facilitating the formation of secondary aerosols. Consequently, the interplay between the protective mountain ranges and the riverine corridors dictates a unique air quality profile, where local emissions are frequently held in place by the surrounding terrain, making the town sensitive to regional pollution shifts and stagnant weather patterns throughout the year.

The air quality narrative in Kasamatsuchō is dictated by the rhythmic shifts of the Japanese seasons. Spring is often the most challenging period, as the town becomes susceptible to Kosa, the yellow dust transported from the Gobi Desert. These mineral aerosols increase particulate matter levels, often coinciding with seasonal pollen spikes, which can severely irritate the respiratory systems of sensitive groups. As summer arrives, the intense subtropical heat and high humidity trigger photochemical reactions, leading to elevated ground-level ozone. This peak usually occurs during the stagnant, humid afternoons of July and August, making these months less ideal for strenuous outdoor exercise. Autumn brings a welcome reprieve; the shifting wind patterns and cooling temperatures typically clear the basin, resulting in the year's freshest air and optimal conditions for outdoor activity. However, winter introduces a different challenge in the form of temperature inversions. Cold, dense air settles on the valley floor, trapping pollutants from domestic heating and regional traffic beneath a warm layer of air. This phenomenon, common in the Nōbi Plain, can lead to localized smog during December and January. For elderly residents and those with asthma, the winter inversions and spring dust events represent the highest risk periods. Health guidance suggests utilizing air purifiers during these peaks and monitoring regional forecasts. By favoring the crisp air of October and November, residents can maximize their exposure to the cleanest atmospheric conditions the region offers each year.