This is the hardest hike so far and you will experience the effects of altitude on this hike. Once you cross the creek, you will gain about 1000 feet in elevation in about a mile and that is just an indication of how hard this hike is going to be. I had no problem getting all the way to High Creek Trail with no breaks where we took a quick break. The next stop was at the viewpoint past the switchbacks. The altitude started hitting me slowly from this point. Once I got to the section above treeline, I slowed down significantly. The final mile took me more than an hour to hike and I was hydrating myself a lot at this point. This is the first time I was feeling the effects of the altitude. The views from the summit were great. San Jacinto appeared so close from here. The last two miles on the way back were hard. Overall, it was a challenging hike. If you are starting early, I would recommend a fleece along with a pair of light gloves.