Mist spraying is an active cooling technology used to alleviate heat stress during hot summers. However, there is limited experimental research on the relationship between ambient thermal parameters and spray cooling efficiency, as well as the transient and short-term thermal perceptions of local residents. In this study, an intermittent mist spraying system was set up, and environmental measurements, coupled with questionnaire surveys, were conducted under typical high temperature and still air conditions. The aim was to investigate the relationship among environmental factors, spray cooling effects, and dynamic improvements in human thermal perception. The results showed that higher ambient temperatures resulted in a more significant cooling effect, with a maximum value of 5.68 °C. Upon entering the spraying area, people experienced a large perceptual change, with the mean thermal sensation and thermal comfort change covering 73% and 62% of the total change ranges, respectively. This study indicated that the mist spray system can be activated if the ambient temperature exceeds 32.5 °C, helping local residents maintain a physiological state close to slightly hot and neutral comfort. These findings suggest that mist spraying can be applied in environmental design as an outdoor cooling spot to mitigate urban overheating, providing valuable insights for the application of mist spray systems in actual outdoor settings in hot-humid areas.