Plus, Stewart said, Death Valley's heat is dry, which means sweat evaporates quickly and cools the body more efficiently. She knew she'd gotten accustomed to the heat, she said, after she started bundling up on 80-degree days.

Yes, you absolutely sweat in Death Valley, but you may never actually feel wet. Because Death Valley is one of the hottest and driest places on Earth, the relative humidity is often near zero. In these conditions, sweat evaporates almost instantly—a process called evaporative cooling—which is your body's primary defense against the extreme heat. Because the sweat disappears into the air so quickly, your skin can feel bone-dry even as you are losing liters of fluid. This is actually dangerous because it can lead to "insensible water loss," where a person doesn't realize they are becoming severely dehydrated. In peak summer, hikers can lose over a liter of water per hour just through this invisible sweating. It is vital to drink water constantly, as the lack of visible sweat can trick your brain into thinking you aren't in physical distress until heatstroke or severe exhaustion sets in.