The extreme heat poses significant risks to residents and visitors in Phoenix. Prolonged exposure to such high temperatures can lead to heat-related illnesses, including heat exhaustion and heat stroke. Popular hiking trails, including Camelback, Piestewa, and parts of South Mountain, will remain closed from 8 a.m. to 5 p.m. through Tuesday night to prevent heat-related emergencies. Vulnerable populations, such as the elderly, children, and those with pre-existing health conditions, are particularly at risk. Additionally, the lack of overnight cooling increases the danger of heat stress, especially for those without access to air conditioning.