Point-of-use water treatment has received widespread application in the developing world to help mitigate waterborne infectious disease. This study examines the efficacy of a combined filter and chemical disinfection technology in removing bacterial contaminants, and more specifically changes in its performance resulting from seasonal weather variability. During a 12 month field trial in Chennai, India, mean log-reductions were 1.51 for E. coli and 1.67 for total coliforms, and the highest concentration of indicator bacteria in treated water samples were found during the monsoon season. Analysis of variance revealed significant differences in the microbial load of indicator organisms (coliforms and E. coli) between seasons, storage time since treatment, and samples with and without chlorine residuals. Findings suggest that the bacteriological quality of drinking water treated in the home is determined by a complex interaction of environmental and sociological conditions. Moreover, while the effect of disinfection was independent of season, the impact of storage time since treatment on water quality was found to be seasonally dependent.