In southwest Texas, they say it can get "hotter than a goat's ass in a pepper patch." But with the Chisos Mountains rising more than 7,500 feet from the Chihuahuan Desert in the center of the park, and the Rio Grande marking its southern edge, there's plenty of opportunity to cool off. The park's top draw is a series of spectacular limestone canyons, some 1,500 feet deep, that the river has spent millions of years carving.

EXPERT ADVICE: "One of the hidden jewels is Mariscal Canyon," says Greg Henington, owner of Far Flung Outdoor Center, in Terlingua, Texas, who's been guiding the Rio Grande for 21 years. "It's right at the bottom of the Big Bend, wild and remote and not frequently traveled because of how difficult it can be to get to." Hire either Far Flung or Big Bend River Tours—both can take you to the park's most intimate canyon, which features ten miles of Class II rapids inside 1,400-foot walls that narrow to only 50 feet in places.

CRASH PAD: After a few days in the canyon, treat yourself to a night in the mountains (and a hot shower) at one of six stone cottages at the Chisos Mountains Lodge, in the middle of the park, about a three-hour drive from the Mariscal take-out. From $115 per cottage; chisosmountainslodge.com

DETAILS: nps.gov/bibe, 432-477-2251; Far Flung Outdoor Center, ffoc.net; Big Bend River Tours, bigbendrivertours.com