Wildfires have forced evacuations for visitors and staff at two national parks in the U.S. West as the summer monsoon season brings increased lightning to the arid region.

Black Canyon of the Gunnison National Park, about 260 miles southwest of Denver, closed until further notice after lighting strikes sparked blazes on both rims, park officials said. The Grand Canyon’s North Rim in Arizona also closed because of a wildfire on adjacent Bureau of Land Management land near Jacob Lake.

The wildfire on Black Canyon of the Gunnison’s South Rim ignited Thursday and has burned 2.5 square miles with no containment of the perimeter. The smaller blaze on the North Rim was out as of Friday, according to an incident map.

The conditions there have been ripe for wildfires with hot temperatures, low humidity, gusty winds and dry vegetation, the park said, adding that weather remained a concern Friday.

Fire danger has ramped up in the West as drought conditions have worsened across several states.

— The Associated Press