On a military base, a black flag is bad news. That means it's too hot outside to do anything strenuous, so training and missions are put off until conditions improve.
As the climate changes, there could be plenty more black flag days ahead, especially in Florida, a new analysis from the Union of Concerned Scientists found. America's military bases could see an average of an extra month of dangerously hot days by mid-century. In Florida, they could quadruple.
Pentagon data shows heat-related illnesses and injuries are on the rise in every branch of the military. Last year, nearly 2,800 troops suffered heatstroke or heat exhaustion, a roughly 50 percent jump from 2014.
"I think most of us, if we hear there are tens of thousands of cases of heat stress in our troops every year, our minds would go to where they were deployed," said Kristy Dahl, a senior climate scientist at UCS and the lead author of the study. "But more than 90% of the military cases of heatstroke happened right here at home."