The extreme heat in San Diego County during August poses serious health risks, including dehydration, heat exhaustion, and heatstroke, particularly for hikers and outdoor enthusiasts. Pets are also at risk, as they can overheat easily and suffer burns from hot pavement. The closure of the parks aims to prevent heat-related incidents and ensure public safety. Visitors to other open parks are advised to exercise caution and follow safety guidelines to minimize risks associated with high temperatures.