Extreme high temperature poses significant threats to public health. Its slow-onset nature allows people to perceive discomfort and protect themselves from negative health consequences, but higher risk perception does not necessarily lead to precautions. Our study understands this gap by arguing that subjective heat-health symptoms are more direct motivations for some heat adaptive behaviours. Through a survey into households (n = 2008) in Taiwan, we assess negative perception of heat impacts during hot days against demographic and socio-economic factors and their relationship with adaptive behaviours. The results show that the frequency of feeling moody and ill varies with age, gender, and health condition, which is also connected to the use of umbrellas and hats. Older people, diabetic patients, and men tend to be less sensitive to high temperature, leaving them with higher heat risk. A sign of biophysical acclimatisation and adaptation of behaviours was found with people frequently working outdoors. They do not necessarily experience discomfort more frequently, but are more likely to use umbrellas and hats. Also, electricity cost may outweigh cooling benefits from using air conditioning in low-income and ethnic minority groups. These results reflect the subtropical Asian context, reinforcing the importance of biophysical as well as socio-cultural components in shaping heat vulnerability of individuals and the need for comprehensive and targeted policy interventions.