Warm Summer Nights Are Becoming the New Normal in U.S. Cities

This summer, many U.S. cities are struggling with something new: nights that never really cool down. Climate scientists say nighttime low temperatures are rising faster than daytime highs in most parts of the country. Cities like Raleigh, Memphis, and Phoenix have all seen record warm nights this year. The change may sound small, but experts say it has a big effect on public health.

During the day, people can escape the heat by staying indoors or finding shade. At night, the body normally cools down and rests. But when nighttime temperatures stay high, the body never gets that break. Doctors say this raises the risk of heatstroke, heart problems, and poor sleep, especially for older adults and people without air conditioning. Hospitals in several cities have reported more heat-related visits during hot nights than during hot days.

Scientists link the trend to a mix of factors. Climate change is raising overall temperatures, and cities trap heat more than rural areas because of pavement and buildings, a problem known as the urban heat island effect. Humidity also plays a role, since moist air holds heat longer after sunset. City planners are now testing solutions like reflective roofs, more trees, and cooling centers that stay open overnight. Experts say adapting to hot nights will be just as important as preparing for hot days.