It is important for engineering applications that we evaluate the thermal environment based on long-term tracking and investment. Methods merging environmental, physiological, and psychological domains to implement a human-centered approach were applied in this study to assess the outdoor thermal environment in a park. The constant influence of humans in the outdoor environment can change people’s physiological, psychological, and thermal responses. Additionally, the relationship between human physiological, psychological, and thermal factors was explored in this study. The results of this study provide the following findings: (1) In summer, subjects’ skin temperature increased by 0.35 to 2.83 °C during a one-hour outdoor test without shelter, while when tree shade was provided, subjects’ skin temperature dropped by 0.50 to 1.87 °C (except for motion segments). (2) In winter, if subjects stayed outdoors for 1 h, their body segments’ skin temperature dropped by a maximum of 7.93 °C. (3) When subjects went outside, in the early stage, their thermal responses fluctuated for a long time. Therefore, TSV, TCV, and TAV should be measured after they stay outdoors for 45 to 55 min in future studies. (4) Different body segments show different sensitivities to hot or cold. Considering this, a new group of formulas for mean skin temperature calculation are proposed with high accuracy (winter: 0.95; summer: 0.89). (5) Data for the one-hour change in different assessment indicators provide a good viewpoint for park design considering multiple aims such as comfort (TCV), pleasure (EVI), and increasing energy (PFI). Overall, this study took Stalin Waterfront Park as a case study, and some suggestions involving landscaping nodes, space types, and facilities are offered. Moreover, this study provides a novel theory and reasonable method that can be referred to in urban planning and landscape design.
