Daytime Heat Is Bad; Nighttime Heat Is Deadly

The sun can be brutal during this record heat wave, but it's overnight temperatures that should really worry you, writes Christopher Mims at Grist. In June, Oman recorded the world's highest minimum temperature ever (107.1 degrees), and in many places, minimum night temperatures are rising even faster than daytime maximum temps. This matters because overnight heat kills more people, writes Mims.

"Everybody normally focuses on that daytime temperature, but that nighttime temperature brings us to a deadly level that is a concern," says the director of the Dallas County Health Department. "At night, there's no cooling off." This is a chief reason why 5,000 people died in Paris during the 2003 summer. What's more, there's a global food connection: Higher daytime temps can increase rice production, but if the crop can't cool at night, harvests drop. (More heat stories.)