Visitors and staff at two national parks in the U.S. West have been evacuated because of wildfires. Officials at Black Canyon of the Gunnison National Park in Colorado say the park closed Thursday morning after lightning sparked blazes on both rims.

The NPS recommends avoiding hiking the Grand Canyon's inner trails between 10 a.m. and 4 p.m., when temperatures are at their peak. Temperatures in the inner canyon can reach over 120 degrees Fahrenheit in the shade, creating "extremely hazardous conditions for hikers," the NPS said.