Climate change profoundly impacts the microbiology and chemistry of drinking water, which affects public health. About 1400 microbes are human pathogens that can lead to adverse health outcomes. This chapter’s microbiological aspects focus on climate change’s effects on these known human pathogens, with a small discussion about emerging and re-emerging pathogens and possible cross-species transmission. This chapter’s chemical aspects focus on climate change’s effects on temperature and flooding, which can release toxic elements from naturally occurring minerals into drinking water supplies. The precautionary principle says that ingesting and using water with anthropogenic chemical contaminants is unacceptable; therefore, climate change’s effects on anthropogenic contaminants are not discussed. The resulting public health effects of these microbiological and chemical changes are discussed. More specifically, this chapter reviews current research on the effects of climate change on water quality and availability and the resulting health outcomes. It highlights the pathways through which climate change affects drinking water, including increased contamination risks and altered water supply patterns. This review also discusses strategies for mitigating these impacts and adapting to the changing environment to protect public health.