Key keywords: weekend summer-like heat, extreme atmospheric humidity, US National Weather Service, heat advisory, heat-related illness prevention, outdoor activity safety, May temperature records, regional weather forecast The U.S. National Weather Service (NWS) issued a nationwide weather alert on Thursday, warning that unseasonably summer-like heat and suffocating humidity will cover more than 70% of the contiguous United States this weekend, pushing high temperatures 15 to 20 degrees Fahrenheit above the long-term average for mid-to-late May. Across the Mid-Atlantic, Northeast, and southern Midwest regions, daily high temperatures are expected to peak between 88 and 95 degrees Fahrenheit, with dew points climbing to 70 to 75 degrees, creating heat index values that will feel as hot as 102 degrees during the hottest hours between 11 a.m. and 4 p.m. local time. As of Thursday afternoon, the NWS has issued heat advisories for 28 states, covering a total population of more than 47 million people, marking the first widespread heat warning of 2024 for most parts of the country. Public health officials have jointly issued guidance with the NWS, reminding vulnerable groups including adults over 65, children under 5, people with chronic cardiovascular or respiratory diseases, and outdoor laborers to take extra precautions over the weekend. Early symptoms of heat-related illnesses include headache, dizziness, excessive sweating, and nausea, and people experiencing these symptoms should move to a cool place, rehydrate, and seek medical help immediately if conditions worsen. Officials also emphasized that residents should never leave children, pets, or elderly people unattended in parked vehicles, even for a few minutes, as interior temperatures can rise to 120 degrees Fahrenheit in less than 20 minutes under direct sunlight. For residents planning outdoor activities such as weekend barbecues, hiking trips, or graduation ceremonies, officials recommend scheduling events before 10 a.m. or after 5 p.m., wearing lightweight, light-colored, loose-fitting clothing, and carrying sufficient water and electrolyte supplements. Coastal areas will see slightly lower heat index values thanks to onshore breezes, but inland areas with poor air circulation will face the most intense heat and humidity. The NWS added that a cold front moving across the Great Lakes region on Sunday night will bring cooler, drier air to most affected areas by Monday, bringing temperatures back to the seasonal average of 65 to 75 degrees for most regions by the start of next week.