The chapter explores the heightened vulnerability of children to extreme temperatures, particularly in the context of a changing climate. It examines the physiological, behavioral, and environmental factors that increase children’s susceptibility to heat- and cold-related illnesses and injuries, such as heat stroke, frostbite, and hypothermia. It outlines the mechanisms of heat exchange, characteristics of thermoregulation of children, and describes other individual factors (physical, behavioral, and socioeconomic) related to the risks of adverse health effects from heat and cold exposure. Practical recommendations are provided for early childhood educators and caregivers to recognize and prevent temperature-related injuries, including appropriate clothing, hydration, physical activity management, and first aid responses. The chapter emphasizes the importance of awareness and preparedness to protect children in both hot and cold environments, particularly during disasters or extreme weather events. It serves as a vital resource for professionals supporting children’s health and safety in a warming and increasingly unpredictable climate.