Perceptions of thermal comfort in heatwave and non-heatwave conditions in Melbourne, Australia

Heatwaves can cause discomfort and illnesses due to heat stress. However, how people perceive thermal comfort and adapt to extreme heat conditions on heatwave days is uncertain. Most outdoor thermal comfort studies have been conducted under non-extreme conditions and very few during heatwaves. For those studies that encountered a heatwave, sample size tends to be small or modelling approaches were used to assess thermal comfort. It is important to understand people's perceptions in relation to the physiological experience during extreme heat, as it would help practitioners apply the extreme heat range of thermal indices in outdoor settings. To understand people's thermal perception and clothing behaviour during a heatwave, we combined meteorological measurements and thermal comfort surveys at two botanic gardens in Melbourne, Australia. The variations in respondents' thermal comfort and clothing are assessed during heatwave and non-heatwave conditions, where temperatures during heatwave conditions exceeded 36°C. We observed that local visitors felt significantly hotter and wore less clothing for the same ranges of the Universal Thermal Climate Index (UTCI) during heatwave than non-heatwave conditions. Thus, we suggest that thermal expectation influences changes in thermal perceptions and clothing, even over the course of several days to a week.