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At an urban site in Kenitra, Morocco, two aerosol size fractions (PM_2.5 and PM₁₀) were sampled for four seasons to characterize the seasonal trends of particulate (PM) and carbonaceous (BC) aerosols. An in-depth statistical analysis of the lag-effects of meteorology on collected data was investigated using uni- and multivariate linear regression analyses. The results revealed significant seasonal trends for PM₁₀, PM_2.5, and BC. PM concentrations showed the maximum values in autumn (61.4 ± 24.5 µg/m³ for PM₁₀ and 21.2 ± 8.2 µg/m³ for PM_2.5), while the minimum was observed in winter (40.2 ± 17.1 µg/m³) for PM₁₀ and in summer (14.3 ± 3.3 µg/m³) for PM_2.5. High BC concentrations were recorded in summer (6.3 ± 4.2 μg/m³, on average). The relative humidity 1–2 days earlier showed a higher negative correlation with the PM concentrations (except in winter), and the temperature 1–3 days earlier showed a negative correlation with the PM_2.5 in winter and summer and a positive one with the PM₁₀ in autumn. Wind speed was negatively associated with PM₁₀ on the current day in winter and 3 days earlier in summer. However, diverse effects of wind speed on PM_2.5 were observed (negative in summer and positive in spring). These results confirm the important role of meteorology in the formation of urban air pollution with pronounced variations in different seasons.