To inform Clark County residents and visitors about the impact of heat-associated illness and mortality, the Southern Nevada Health District has prepared this report summarizing 2025 surveillance data on heat-associated deaths and emergency department visits. The Centers for Disease Control and Prevention (CDC) define extreme heat as reaching higher than average temperatures or humidity levels for a particular location and time of year. Heat-related illness occurs when the body is unable to adequately dissipate heat, resulting in a rapid rise in core body temperature. Clinical manifestations range from heat exhaustion to heat stroke and may lead to multi-organ dysfunction, including neurologic injury. Older adults, young children, and individuals with mental illness or chronic health conditions are at the highest risk for heat-related illnesses. However, heat-related illness can affect anyone, particularly those engaging in strenuous physical activity in high-temperature environments.