This paper analyzes the relationship between rain intensity and commuters' return home behavior to clarify the extent to which rain affects commuters' departure decisions. Results show that about 60% of respondents changed their departure time. Although weather forecasts predicted torrential rain for the day examined in this study, the percentages of respondents who checked the weather directly or obtained weather information were only 42% and 26%, respectively. In order to statistically analyze the above relationship, an ordered logit model was estimated. The result showed that commuters are likely to change their departure time early when rain intensity is 50 mm/h or more. This result can thus serve as a criterion of commuters' departure decision on days of torrential rain. Additionally, those who obtained weather information while in their destination area and who went home at peak rush hour showed a strong tendency to change their departure time early.