This book provides a comprehensive exploration of methods and insights for understanding and improving thermal comfort in outdoor environments. Outdoor thermal comfort has become an increasingly critical area of research, especially in the context of climate change and urbanization. It presents cutting-edge techniques for measuring environmental parameters, such as radiant temperature and ground temperature, while introducing innovative modifications to established thermal indices like the Physiological Equivalent Temperature Index (PET) and the Universal Thermal Climate Index (UTCI). The book also delves into human factors such as metabolic rates and behavioral adaptations, offering a nuanced perspective on the interaction between individuals and their thermal environment. Distinguished by its integration of real-world case studies, validated models, and practical design guidelines, this book features a rich array of illustrations, comparative analyses, and novel frameworks for urban cooling and heat stress mitigation. Its value lies in equipping readers with the tools to assess thermal comfort more effectively, design climate-resilient spaces, and promote safer outdoor environments. Targeted at researchers, urban planners, environmental engineers, and policymakers, this book serves as both a foundational resource for academic study and a practical guide for professionals addressing the challenges of outdoor thermal comfort.