Whew!  I think this was one of the hardest hikes I've done so far.  For me, it seemed a surprisingly harder one than hiking to the top of San Gorgonio.  I had to take a lot more trail breaks than I usually do.  Which was probably due to a combination of the first two miles of Oak Grove Trail being an unrelenting uphill slog, and the sun really heating up the landscape as soon as daylight hit.  I usually take a minimum of four liters of water when I go hiking, and by the time I returned to the trail head, almost all that water was gone.  Other than that, this was a beautiful hike, with amazing views throughout, of San Jacinto, San Gorgonio, and San Antonio (Baldy), almost the whole length of the trail.  The bugs didn't really become a problem until after the sun had been up a few hours.  And, there was a bit of a breeze that was intermittent, along the trail, so the hike was relatively pleasant, overall.

This region is really starting to heat up, so I would suggest starting before first light, if you can, and, if you do get caught on the trail after 3:00 pm, take a nap, until the sun has moved a bit lower in the sky.