The extreme heat poses significant risks to hikers and outdoor enthusiasts in Phoenix, with temperatures forecasted to remain above 110°F (43°C) for several days. Heat stroke, characterized by symptoms such as confusion, dizziness, and dangerously high body temperatures, can be life-threatening if not treated promptly. Multiple rescues occurred on Sunday, including another hiker at Piestewa Peak who experienced dizziness but refused hospital transport. The closures of popular trails aim to mitigate risks during the hottest parts of the day.