Based on daily temperature, relative humidity, and wind speed data from 19 national meteorological stations and 308 regional automatic weather stations in Hainan Island between 2010 and 2024, this study investigates the spatiotemporal distribution characteristics and influencing factors of human thermal comfort using methods such as linear trend analysis and cumulative anomaly. The main findings are as follows: (1) Throughout the year, the thermal comfort condition in Hainan Island is dominated by “comfortable” and “hot-uncomfortable” levels, accounting for 65.7% and 33.5% of the days, respectively, while “cold-uncomfortable” days make up less than 1%. Comfortable days are mainly concentrated from October to April of the following year, whereas hot-uncomfortable days are prevalent from May to September. (2) Spatially, the number of comfortable days exhibits a pattern of “higher in the central region and lower in the surrounding areas”, while the distribution of hot-uncomfortable days shows the opposite trend. (3) From 2010 to 2024, the annual average number of comfortable days and cold-uncomfortable days displayed a significant decreasing trend, while hot-uncomfortable days showed a significant increasing trend. (4) Temperature is the primary factor influencing the human comfort index. Since 2019, rising temperatures have been associated with a reduction in comfortable days and a notable increase in hot-uncomfortable days. (5) The use of high-density station data significantly improved spatial accuracy, enabling the precise identification of regions such as western Qiongzhong and the northern part of Wuzhishan, where the annual number of comfortable days exceeds 280 and favorable comfort conditions are maintained even during summer. These findings provide refined climatic evidence to support regional health and wellness planningg.