Rising Nighttime Temperatures Trim Global Sleep Hours, Study Finds

Research shows that hotter nights are shaving an average of 56 sleep hours per person each year, with climate change accounting for roughly six of those hours.

Extreme heat is not only a daytime hazard; it is also keeping nights uncomfortably warm, eroding sleep time across the globe. Climate Central’s latest analysis estimates that from 2020 to 2025 individuals lost an average of 56 hours of sleep each year, with climate change responsible for about six of those hours. In the United States, cities that already endure high temperatures—particularly in Arizona, Florida and Nevada—experienced the steepest declines, while desert locales like Flagstaff, Reno and Salt Lake City showed the largest increases in lost sleep since the 1970s. Internationally, residents of Saudi Arabia, the United Arab Emirates and India reported up to 87 and 93 lost sleep hours annually, respectively.

Ariane Middel, an urban climatologist at Arizona State University, explains that persistent heat forces the body to work harder to cool down at night, reducing restorative rest. Kristina Dahl, Climate Central’s vice president for science, warns that even modest sleep loss can aggravate health issues such as heart disease and obesity. Access to air-conditioning, present in about 93% of U.S. homes, eases the problem, but many low-income or poorly ventilated households remain vulnerable. Practical steps like shading windows, using fans or opening windows when outside temperatures dip can help, though extreme heat waves—like Phoenix’s recent 115°F daytime high and 97°F low—limit those options.