Extreme heat deteriorates health, increasing morbidity and mortality. Its widespread impact can cause surges in healthcare demand, leading to hospital congestion. This paper offers the first analysis that separates the direct health effects of extreme heat from the indirect effects caused by hospital congestion. Using data from Mexico’s largest healthcare subsystem, we find that higher temperatures increase emergency department (ED) visits and hospital admissions. At daily maximum temperatures above 34°C, ED visits rise by 7.5 percent, and hospitalizations by 4 percent.