With summer officially underway, millions of Americans are facing another week of heat advisories across the Northeast, Midwest, and South. As temperatures worldwide continue to rise due to climate change, the limits of the human body’s ability to deal with excess heat are being tested. Last week, more than 1,000 people died on a pilgrimage to Mecca in Saudi Arabia amid … [Read more...] about As the U.S. heat wave drags on, experts warn of deadly ‘wet-bulb’ temperatures. Here’s what those are.