THM analysis results for water samples taken from the raw water and water treatment plant during the 2018 flood event. The water samples were chlorinated at 1,3,5 mg/L free chlorine. This dataset is associated with the following publication: Yang, J., C. Buahin, and R. Murray. Modeling and assessing chlorinated and brominated THM formation for water treatment adaptation against hydroclimatic impacts. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, NETHERLANDS, 999: 180312, (2025).