Despite the measures put in place, every heat wave leads to excess mortality and morbidity. A quantitative study of the general population conducted in 2015 revealed a lack of perception of personal risk, fragmented knowledge of recommended actions and warning signs, and a lack of awareness regarding at-risk groups, despite the perception that people were well-informed. This new study aims to explore the motivations for adopting—or failing to adopt—appropriate behaviors during heat waves. A qualitative study was conducted with 74 individuals aged 18 to 64 residing in a department under an orange or red heat wave alert in 2019. Focus group interviews were designed to understand collective perceptions of heat waves; individual interviews addressed personal dimensions (perceptions, difficulties) affecting the experience of these episodes. Participants reported being well-informed about protective measures but less so about warning signs and at-risk groups. Adherence to protective measures was influenced by the perception of personal risk. Objective barriers such as working conditions or lack of awareness of existing resources (maps of cool places, drinking water stations, etc.) were identified. The lack of perceived personal risk is partly associated with the belief that health risks during a heatwave are linked to a pre-existing condition (age, medical condition), rather than to overexposure to heat. The barriers to adopting certain protective measures highlighted the need to strengthen communication about existing measures and to study the feasibility of adapting working conditions through regulatory means.