The upper areas of the Skyline are in the State Park. I know because the Rangers pulled a bunch of fixed climbing anchors off Coffman Crag years ago and the trail goes right by Coffman. Lower areas are Aqua Caliente and BLM.
The last time the State Park closed like this it was closed until the first winter snowfall. I think it was in 2003 or 2004. The fire danger was too extreme and this year is worse. I haven't been up Skyline lately (too many people these days) but I would imagine it's all pretty dry up there.
For someone looking for a hard hike in the area I would recommend Rabbit Peak. I actually think Rabbit Peak is harder than Skyline.
Another fun hike is from the Coachella Valley to Key's View in Joshua Tree.
It's not as challenging as the others but it's less traveled.
