A mix of high temperatures, gusty winds, low humidity, and dry vegetation has fuelled the fire's swift advance in Arizona, officials say.

Visitors and staff at two national parks in the U.S. West have been evacuted 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 North Rim of the Grand Canyon is closed "until further notice" as a wildfire rages in the area, park rangers announced on Thursday.