The first recorded heat advisories in the United States emerged in the late 19th century, when local weather services began issuing notices based on surface temperature thresholds. These alerts were simple, often limited to a single day’s maximum and issued only when temperatures surpassed a fixed benchmark.

As meteorological science advanced, the 20th century saw the incorporation of humidity, wind, and population density into heat advisory frameworks. By the 1970s, the National Weather Service (NWS) introduced the Heat Index, a composite metric that better reflected perceived heat stress. This evolution marked a shift from reactive to proactive warning systems.