The closures will take effect at 11:59 p.m. Tuesday and last through Sept. 17, according to the U.S. Forest Service.
"We do not take this decision lightly but this is the best choice for public safety," said Regional Forester Jennifer Eberlien. "It is especially hard with the approaching Labor Day weekend, when so many people enjoy our national forests."
The closure is designed to reduce the possibility of people being trapped in the forests when wildfires break out, as well as reduce the potential for new fires to start.
The closure includes the Angeles National Forest, accessed by hikers from the Mt. Wilson trailhead in Sierra Madre.
"I'm kind of disappointed because...I'm safe up there. I'm not going to do anything to cause problems," said Kristine Spicer-Cardenas, who added that she'll have to find somewhere else to run.
The order provides exemptions for certain permit holders, emergency crews, utility companies and landowners.
More about the order can be found here.
The Forest Service says more than 6,800 wildfires have burned 1.7 million acres across California.