Earth’s warming climate is causing heat waves to become more frequent, longer lasting, and hotter, while occurring in locations unaccustomed to such weather events. Extreme heat events (EHEs), such as those in the western United States, India, Pakistan, Central Europe, and other locations in recent years, are one of the deadliest consequences of climate change. EHEs cause excess morbidity and mortality directly from heat illness, aggravation of comorbid conditions, and exacerbation of the damaging health effects of social factors as well as indirectly from corollary events such as wildfires and air pollution. Climate change–related EHEs are projected to worsen for at least the next 3 decades, necessitating that health systems be prepared to meet a growing burden of heat-related illnesses and become more heat resilient, as well as to reduce health care–related climate impacts. In this article, the authors discuss the health effects of EHEs and provide illustrative examples of what health systems can do to promote climate readiness and heat resiliency.