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Mékhé is situated within the Thiès region of Senegal, serving as a vital crossroads in the heart of the peanut basin. Its geography is characterized by the vast, semi-arid Sahelian plains, where the terrain is predominantly flat with subtle undulations. Positioned away from the immediate cooling influence of the Atlantic coast, the city experiences a more continental climate than Dakar, which directly impacts its atmospheric stability. The surrounding landscape is a mosaic of scrubland and extensive agricultural zones, where the urban-rural gradient is porous, blending residential clusters with farming plots. This proximity to agricultural land introduces significant organic particulate matter into the air, particularly during land clearing phases. Elevation remains relatively low, allowing for the unimpeded movement of air masses across the plateau. The region lacks major bodies of water, meaning there is little natural moisture to scrub pollutants from the air during the dry season. Instead, the city is exposed to the sweeping winds of the interior. Urban character is defined by low-rise structures and unpaved roads, which contribute to the suspension of mineral dust. The regional position makes Mékhé a transit point for goods moving toward the coast, introducing vehicular emissions from diesel trucks into an otherwise rural atmospheric profile. Consequently, the interplay between the arid soil, agricultural practices, and transit traffic creates a unique air quality profile dominated by crustal dust and seasonal biomass smoke, reflecting the delicate balance of its Sahelian environment. The city's layout further concentrates these elements within its small, growing urban residential core.

The air quality in Mékhé is dictated by the stark dichotomy between the dry and wet seasons. From November to May, the city is dominated by the Harmattan, a northeasterly trade wind that transports vast quantities of mineral dust from the Sahara Desert. During these months, pollution peaks as fine particulate matter saturates the atmosphere, often creating a hazy veil that reduces visibility and irritates the respiratory system. Temperature inversions during the cool winter mornings can trap these pollutants near the ground, exacerbating the effect. Conversely, the wet season, spanning from June to October, brings the monsoon rains which act as a natural atmospheric cleanser. Precipitation effectively washes particulates from the sky, leading to the cleanest air of the year. However, the transition periods are critical; late dry season often coincides with agricultural burning of peanut stalks, releasing plumes of carbonaceous smoke. For sensitive groups, including children and the elderly, the Harmattan months are the most hazardous, requiring the use of masks and limited outdoor exertion during peak dust events. The most favorable period for outdoor activity is the height of the rainy season, when humidity is high and dust is suppressed. Health guidance emphasizes hydration and respiratory protection during January and February when the Saharan influence is strongest. By understanding this cyclical pattern, residents can better navigate the environmental risks associated with the Sahelian climate and the specific agricultural rhythms of the Thiès region. This predictable cycle allows for better health planning and the implementation of targeted protective measures.