In order to realize scientific risk assessment of public opinion on extreme rainstorms, this paper proposed a public opinion risk assessment method of extreme rainstorm disasters based on three-way decisions under the event system theory. From the perspective of event system theory, this method determined the life cycle of public opinion and built indicators for evaluating the risk of public opinion on extreme rainstorm disasters by integrating three dimensions: time, space, and strength. Meanwhile, this paper integrated review helpfulness with hesitant intuitionistic fuzzy sets, effectively quantifying public opinion preferences regarding risk assessment indicators of public opinion. On this basis, the paper extended the three-way decision method to classify public opinion risk into five levels, achieving a scientific assessment of public opinion risk towards extreme rainstorm disasters. Using actual cases and comparative analyses, the effectiveness and adaptability of the risk assessment model of public opinion towards extreme rainstorm disasters were verified. The results show that the proposed method not only successfully realizes the scientific selection of public opinion risk assessment indicators with respect to extreme rainstorm disasters and the effective quantification of public opinion preferences, but also alleviates the decision-making errors caused by the information and cognitive limitations of existing assessment methods to a certain extent.