Last month was the hottest June on record in North America, with more than 1,200 daily temperature records broken in the final week alone. But overlooked in much of the coverage were an even greater number of daily records set by a different — and potentially more dangerous — measure of extreme heat: overnight temperatures.
On average, nights are warming faster than days across most of the United States, according to the 2018 National Climate Assessment Report. It’s part of a global trend that’s being fueled by climate change.
Unusually hot summer nights can lead to a significant number of deaths, according to climate scientists and environmental epidemiologists, because they take away people’s ability to cool down from the day’s heat.