A heat advisory is a warning issued by the U.S. National Weather Service when temperatures or the heat index reach levels that are potentially hazardous to human health. The exact criteria for issuing this alert can vary by location, but it is typically triggered when temperatures are significantly above normal and coupled with high humidity. These combined conditions pose a serious risk of heat-related illnesses, such as heat stroke, which can be life-threatening. For example, on July 8, 2020, the National Weather Service office in Pittsburgh, Pennsylvania issued a heat advisory for portions of southwest Pennsylvania, east central Ohio, and West Virginia, forecasting heat index values up to 102°F. The advisory urged residents to drink plenty of fluids, stay in air-conditioned rooms, and check on relatives and neighbors, while also warning that children and pets should never be left in vehicles. It further advised outdoor workers to take extra precautions and stressed that heat stroke is a medical emergency requiring an immediate call to 911.