Death Valley National Park earns the biggest temperature swing in our series on the best national parks to visit this fall, and it's the swing that makes the park enjoyable during this season. Highs slide from the 120s to the upper 70s by November, one of the most dramatic seasonal coolings of any national park in the country. That drop of nearly 40 degrees turns the hottest place on Earth into somewhere you can genuinely walk around, explore salt flats and dunes, and hike trails that are near-impossible to tackle in summer.