The season has a significant impact on the presence of microorganisms in water sources. Various contaminants and bacteria are transported into water sources by heavy rains. Because of the poor microbiological condition of such water bodies, regular monitoring is required. Routine monitoring, on the other hand, considers the microbial quality of the water column.The objective of this research was to investigate the microbiological quality of Nainital Lake in Uttarakhand, using Escherichia coli as a faecal indicator organism, and examine how seasonal fluctuations (dry and rainy seasons) affected its abundance. During 2018 and 2019, samples were taken from Nainital Lake sampling sites during the summer (dry) and rainy (wet) seasons and presence of E. coli was examined using various media, IMViC and catalase tests. E. coli was discovered at all of the locations and its concentration was influenced by seasonal variations. In both years, the cfu/ml count during the rainy season was observed higher in comparison to count during the summer. The transmission of this bacteria into the water column as a result of events such as floods or human activities might harm the health of those who consume untreated lake water for recreation and other domestic reasons. As a result, community education for health care practitioners and the general public about the proper use of lake water is essential. In order to preserve human health and other aquatic life, regular water quality monitoring is also required.