The National Oceanic and Atmospheric Administration revealed data that shows 2016 had the hottest summer nights on record.
The nights over the summer had an average temperature of 60.8 degrees, which was 2.4 degrees higher than normal, reported USA Today. According to climate scientist Jake Crouch, the higher temperatures were a result of unusually high levels of humidity coming from the Gulf of Mexico.
Overall, the summer of 2016 was the fifth-hottest on record. The average temperature of the lower 48 states was 73.6 degrees, which is 1.5 degrees above normal, according to the NOAA.
Higher temperatures are often attributed to climate change. But climate scientists believe there might be different reasons for why nighttime temperatures appear to be rising faster than daytime temperatures.
One reason could be more clouds keeping hot air close to the Earth's surface, reported Time. Another reason, as Crouch suggested, could be more humidity. But other scientists told Time that the increased humidity might be due to changes in agriculture that have led to more irrigation.
Although the nights are only a few degrees hotter than normal, the higher temperatures could pose risks to people susceptible to heat stroke because the evenings aren't giving the same level of relief from the hot days.
“When it’s hot out, your body has to work pretty hard to keep itself cool,” Brooke Anderson, an epidemiologist at Colorado State University, told Time. “If it gets very hot at night and you continue to be exposed to it, your body does not get a chance to rest.”
Although a few degrees might not seem like a big deal, climate scientists say they are.
“People might think, ‘who cares about night? It’s cooler,'” said Ken Kunkel, a senior scientists at NOAA’s National Centers for Environmental Information. “But don’t ignore the increase in night time temperatures ... they matter.”