Extreme heat events, increasing in frequency and intensity due to climate change, highlight the need for thermal resilience in buildings. Current designs and operations of buildings often prioritize energy efficiency and occupant comfort, and heat stress indices are mostly generalized in their assessment. In other words, this focus may not fully address building and occupant heat stress and resilience during extreme environmental conditions introduced by, for example, climate change. This study is formulated to address this research gap by investigating individual thermal resilience under extreme indoor environmental conditions. We posit that individuals have unique mechanisms to deal with extreme heat stress, and our investigation involved four healthy adults exposed to temperatures ranging from 24 ℃ (75.2°F) to 40 ℃ (104°F) and humidity levels between 17% and 34% in a controlled climate chamber for two hours. Then, they had a resting period of 20 min in a resting room with a temperature of 23 ℃ (73.4°F). Results demonstrate significant differences in heat stress response among subjects. The dynamic nature of individual heat stress response, as evidenced by variations in heat intensity, thermal sensation, and thermal preference responses were revealed in this study. We used the K-Nearest Neighbors (KNN) algorithm with three neighbors and a five-fold cross-validation process to see the potential of predicting changes in one subject’s thermal sensation as a preliminary demonstration. This method attained an accuracy of 0.96, coupled with a corresponding F1-score of 0.95. These findings highlight the necessity of reframing building and occupant thermal resilience through personal assessments and the technology needed by underserved communities to correctly measure their response to heat stress and housing performances, especially in the face of a changing climate.