An application of wavelet analysis is done with the total monthly rainfall data of Matsuyama city, in order to analyze the rainfall variability observed in such an area. Besides the rainfall variability analysis, the main frequency components in the time series are studied by the global wavelet spectrum, revealing that the monthly rainfall in Matsuyama city is composed mainly by an annual frequency. Thus, the modulation in the 8-16-month band is examined by an average of all scales between 8 and 16 months, giving a measure of the average monthly variance versus time, where the periods with low or high variance could be identified.