The O3 concentration levels at a rural site (Mwetemo village, Bagamoyo) were analyzed based on several dif- ferent scales, such as hour, month, and season, from December 2013 to October 2014. Figure 4 shows monthly mean O3 concentrations with error bars showing standard deviation. The monthly mean O3 concentrations ranged from 9 ppb to 17 ppb, with the lowest levels in April and the highest levels in December. There was a small fluctuation of ozone concentrations in the months of March through May (MAM), compared to the other months. Also, the mean monthly ozone concentration was the lowest in MAM. This may be the result of a pe- riod of heavy rain, when air is much cleaner.