By 2050, a bad night’s rest could be almost twice as common as it is now. That’s the conclusion of the largest study yet on sleep and temperature, which finds that climate change could make restless nights more frequent. Previous studies showed that higher core body temperatures are linked to shoddy slumber, and that nighttime temperatures are warming faster than daytime temperatures. To see if climate change could make it worse, scientists investigated government surveys from 2002 to 2011 that asked 765,000 people how often they experienced insufficient rest or sleep during the past 30 days. Combining those responses with city and date-matched weather data, the team discovered that nighttime temperatures 1°C above the monthly average resulted in about three additional nights of inadequate sleep, they report today in Science Advances. The model suggests that if the average temperature were always raised 1°—a likely scenario for our warming world by 2050—the U.S. would see about 110 million additional sleep-deprived nights annually. Individuals making less than $50,000 a year were about three times more likely to suffer poor sleep on warmer-than-average nights compared with wealthier people, and those over age 65 were affected twice as often as younger individuals. The researchers were careful to note multiple limitations to their study, which didn’t account for temperature variations within cities or quantify sleep loss by the hour. But the implications are enormous. About one-third of adults already report trouble sleeping, and inadequate sleep is linked to a laundry list of health complications, including a weakened immune system, cardiovascular disease, diabetes, and depression.