Saving Lives at the Grand Canyon, One Salty Snack at a Time Some key points from the article:
1. Rangers at the Grand Canyon now use a "P-SAR" approach, "preventive search-and-rescue, to try to intervene with hikers before they get in trouble on hot days.
2. The "drink, drink, drink" message of focussing on water consumption alone, popular in the 1990s, has been revised to add attention to salt consumption as well, to avoid hikers becoming "hyponatremic."
3. 95 deg F (35 deg C) is a significant danger point, beyond which the body can only cool itself by sweat evaporation. After several hours, most people simply can't sweat enough to cool down anymore.