Assessing the Public Perception of Thermal Indices for Heat-Related Advisories: A Case Study in Singapore

Heat-related advisories often use thermal indices to guide public action on coping with heat. With over 165 thermal indices developed to assess outdoor thermal comfort, these tools integrate a wide range of variables; meteorological factors (e.g., air temperature, humidity, wind speed, solar radiation) and personal/physiological factors (e.g., metabolic rate, clothing insulation). Each index offers a unique approach to evaluating human thermal perception, reflecting the complexity and diversity of outdoor environments and individual experiences. The evaluation and selection of the appropriate index relies largely on scientific robustness and ease of operation. However, indices that meet these scientific criteria may not be effectively communicated to the public due to their technical nature and complexity. 
In this study, over 400 individuals were surveyed across three outdoor sites on the Singapore Management University’s city campus aimed to explores the precision and accuracy of commonly used thermal indices (Air Temperature, Heat Index, Mean Radiant Temperature, Physiologically Equivalent Temperature, Universal Thermal Climate Index, and Wet Bulb Globe Temperature) in relation to the perceived air temperature, and thermal comfort of adult Singapore residents. The study compared these indices against individuals' subjective thermal perceptions and assessed the level of public awareness regarding these thermal indices and their understanding of the variables that contribute to each index, and their awareness of the Singapore Heat Stress Advisory. This study could potentially add to the evaluation criteria when cities select or review the appropriateness of thermal indices for heat-related advisories.