This summer was the hottest in American history, with many cities experiencing more days of temperatures above 100 degrees Fahrenheit than ever before. According to AccuWeather, the top five cities with the most triple-digit temperature days were primarily in the South. Dallas, Texas, led the list with 52 days of temperatures above 100 degrees, more than double its historical average and significantly higher than the seven recorded in 2025. Austin, Texas, came in second with 48 scorching days, compared to fewer than half that number in 2025. Oklahoma City ranked third, followed by Tulsa and Wichita, all of which recorded far more 100-degree days this year than in 2025. Across the country, many cities have tied or broken annual records for the number of days with temperatures at or above 100 degrees. In Lander, Wyoming, the number of days with temperatures above 100 degrees tied its historical record of three. Similarly, New York City's Kennedy Airport and Atlantic City also tied their respective records, with the latter having four days of 100-degree heat. Miami recorded its all-time high of 100 degrees this summer, a milestone that has only occurred once before. In Colorado, the state saw 27 days with temperatures over 100 degrees, surpassing the previous record set in 2002. The extreme heat can be attributed to major heat domes, which are large areas of high pressure that trap hot air and create prolonged periods of high temperatures. A significant heat dome over the South in September contributed to the record-breaking temperatures. Even as the summer heat begins to fade with the arrival of fall, the effects of climate change and a strengthening super El Niño climate pattern are contributing to warmer temperatures across the country. These changes have been observed in shifts in fall foliage, with leaves changing color later than usual, and in the extension of hurricane and wildfire seasons. The rising temperatures have serious implications for public health. Heat is already the leading cause of weather-related deaths in the United States, and any temperature above 80 degrees Fahrenheit can pose a danger to human health, according to the National Weather Service’s Heat Index. As the climate continues to change, the frequency and intensity of extreme heat events are expected to increase, putting more people at risk, particularly the elderly, young children, and those with preexisting health conditions.