#18: Zion National Park During Peak Heat
Shade in a canyon can be deceptive. A trail may begin beside a cool wall or near the Virgin River, then turn into direct sunlight with several miles still ahead. Summer daytime temperatures regularly exceed 100 degrees in Zion Canyon, while tall sandstone walls can limit airflow in certain areas. July through September adds monsoon storms and flash-flood danger, particularly in narrow canyons. That means visitors must think about water from two opposite directions: carrying enough to drink and avoiding places where sudden flooding may occur.
