["Sociological Forum, Volume 41, Issue 1, Page 60-75, March 2026. ", "\nABSTRACT\nThis article explores the concept of thermal security as an analytical lens for understanding how individuals experience, interpret, and respond to urban heat waves. Drawing on Anthony Giddens' notion of ontological security, thermal security refers to the continuity and reliability of safe and comfortable thermal conditions that allow people to sustain everyday routines and a sense of existential stability. Through a systematic review of 26 qualitative studies, this paper synthesizes empirical insights from a wide range of geographic and cultural contexts. It identifies five key dimensions of thermal security—exposure, access, affordability, emotional impact, and coping strategies—and shows how these are shaped by intersecting social, material, and infrastructural inequalities. The review argues that qualitative research, often undervalued in climate studies, offers fine‐grained and situated knowledge essential for understanding the lived consequences of heat stress, particularly among vulnerable populations. By bridging ecological, emotional, and sociotechnical dimensions, the concept of thermal security provides a comprehensive framework for assessing adaptation needs and justice‐oriented climate responses in urban contexts.\n"]