Urban heat, the combined effect of heatwaves and urban heat islands (UHIs), is a severe challenge for many cities around the world. While there have been numerous studies on urban heat, society’s understanding of it is still insufficient, hindering its mitigation and adaptation. This paper aims to investigate people’s vulnerability to, and perception, awareness and knowledge of, urban heat. A questionnaire survey was conducted with 562 respondents in the hot and humid city of Chongqing, China in the summer of 2020. Data were analysed using descriptive statistics, Mann-Whitney U test, Kruskal-Wallis H test and logistic regression. Results indicated that urban heat is generally understood as having a moderate severity, while there is limited knowledge of heat-related risks. The perceived heat-related psychological impacts are more severe than physiological impacts. There is limited awareness and knowledge of heat-impact reduction methods. Nevertheless, people’s awareness, perception and knowledge of urban heat increase once they suffer heat-induced impacts, indicating exposure/experience-driven awareness and knowledge. Moreover, climate injustice among different groups (e.g. gender, age, education, income, health) of people related to heat challenges was identified. People’s perception, vulnerability, awareness and knowledge increased with age, but interestingly decreased with increasing education level and improved health conditions. Economic factor was not critical to heat-related responses. Men could be more vulnerable to physiological symptoms and daily functioning than women. The results of this study provide an understanding of urban heat perception and adaptive knowledge, enabling practitioners and policy makers to formulate effective urban heat mitigation and adaptation policies and regulations.