Ground level ozone (O3) is the most significant secondary air pollutants in Malaysia, and this air pollutant exhibited different variations during daytime and nighttime due to differences in photochemistry. This utilizing seven variables (O3, NO2, NO, SO2, PM10, temperature, and relative humidity) secondary data acquired from the Air Pollution Division, Department of Environment Malaysia. The nighttime data (7 p.m. – 6 p.m.) on March and December 2015 were used to represent the dry and wet months, respectively. Box and whisker plots were used to show the variation of nighttime O3, NO2, NO, SO2, PM10, temperature, and relative humidity during the dry and wet months. Results suggested that there are variations among the selected variables between dry and wet month with temperature, O3, NO2, and PM10 showed higher value during dry month compared to wet month. Meanwhile, relative humidity, NO, and SO2 showed the opposite result.