Outdoor thermal environment has become a critical factor in both architecture design and urban planning field, and some researchers argued that the reactions of different people to outdoor environments should be considered, for instance, age, gender and so on. While tourists are exposed to an outdoor environment of unfamiliar climate in a short period, and their clothing and activity level which are supposed to be different from local people are surely to influence their outdoor thermal environment experiences, which need to be clearly revealed. This study investigated 1740 samples in Harbin, China, and 844 samples in summer and 896 samples in winter were gathered. The samples were divided into local people and tourists, and their reactions of clothing insulation and activity level to the outdoor environment were studied. The results show that the local people and tourists reacted to the outdoor environment by clothing insulation in both summer and winter, and the tourists dressed more clothing in winter than the local people. The tourists’ activity level was not influenced by the outdoor thermal environment, which should be due to a pre-made plan when they traveled to a new place, as for the local people, their activity level was influenced by the outdoor environment in summer, higher air temperature led to higher activity level, and in winter, it seems that they did not react to the outdoor environment clearly, and they preferred to do more activities in late morning and afternoon, to avoid the very cold early morning maybe.