Key keywords: hot and humid afternoon, summer heat advisory, high humidity health risk, heat exhaustion prevention, outdoor activity restriction, 2024 summer weather warning, vulnerable groups heat protection, peak electricity grid load The National Weather Service (NWS) issued a level 3 heat advisory at 8 a.m. local time on Thursday, warning that most regions across the central, southern and eastern U.S. will experience record-breaking hot and humid conditions this afternoon, with actual temperatures reaching 95 to 102 degrees Fahrenheit, and heat index values soaring to 110 to 118 degrees between 1 p.m. and 6 p.m. local time. Meteorologists explained that the unusual heat is driven by a stagnant subtropical high pressure system that has been lingering over the continent for 12 consecutive days, combined with moist warm air flows blowing in from the Gulf of Mexico, which pushes relative humidity to above 80% in most populated areas, making the heat feel far more oppressive than dry heat at the same temperature. The NWS emphasized that the high humidity will slow down the human body’s evaporative cooling process, raising the risk of heat cramps, heat exhaustion and even life-threatening heat stroke far higher than ordinary summer heat days. Vulnerable groups including senior citizens aged 65 and above, children under 4 years old, pregnant people, residents with chronic diseases, and people who work outdoors for long periods are listed as the highest risk groups for heat-related illnesses. Local authorities across 37 states have rolled out emergency response measures in line with the advisory: 217 community cooling centers have been opened to the public for free, equipped with air conditioning, drinking water and basic first aid supplies; all public school districts in affected regions have canceled all outdoor after-school activities including sports training, playground activities and off-campus field trips scheduled for this afternoon; construction, logistics and other industries with large numbers of outdoor workers are required to adjust work schedules to avoid peak heat hours, and provide free electrolyte drinks and heatstroke prevention medicines for frontline workers. The U.S. Department of Energy also issued a reminder that the widespread use of air conditioning this afternoon is expected to push the national grid load to a new summer high, urging residents to set air conditioner temperatures at 78 degrees Fahrenheit or higher when at home, and turn off unnecessary electrical appliances to reduce grid pressure and avoid large-scale power outages. Residents are also advised to avoid going out unless necessary between 1 p.m. and 6 p.m., wear loose, light-colored and breathable clothing if they have to go out, drink water regularly even if they do not feel thirsty, and check on family members and neighbors who live alone, especially the elderly, to ensure they are staying cool.