Cooling Season Thermal Comfort in Underground Subway Stations and Cross-Climatic Discrepancies: A Beijing–Suzhou Comparison

Subway stations are typical underground transitional spaces with complex thermal environments. Existing studies often characterize the comfort zone by temperature alone and lack cross-climate comparisons, limiting practical applicability. To address this, the standard effective temperature (SET*) was adopted in this study as the core index to couple multiple environmental and personal parameters. On-site measurements and questionnaire surveys were conducted in summer in Beijing, located in the cold climate zone, and Suzhou, in the hot-summer and cold-winter zone. Based on 410 samples from Beijing, the neutral SET* was 23.37 °C for concourses and 20.43 °C for platforms, with 80% acceptable ranges of 20.37–26.38 °C and 18.4–24.62 °C, respectively. Optimal thermal sensation was slightly cool, reaching −0.503 in concourses and −0.318 on platforms. Cross-climate comparison revealed a systematic warm-side shift for Suzhou passengers from 181 samples: neutral SET* increased to 26.46 °C in concourses and 23.99 °C on platforms, comfort zones shifted upward to 25.00–28.97 °C and 21.90–27.03 °C, and optimal thermal sensation values of −0.153 and −0.262 indicated weaker cool preference and higher heat tolerance. These findings improve understanding of thermal comfort in subway stations and provide guidance for environmental design.