We just got back from backpacking rim-to-rim in the Grand Canyon (5-8 June).  With the exception of the first day when we descended the north rim on the North Kaibab trail, we started the next three mornings, as in on the trail, no later than 5 AM so we were moving through the canyon before the sun entered the canyon deep enough to reach the trail.  In fact we were either finished our hike or extremely close to finishing each day's section before the trail got hot.  Then we set up camp and spent the rest of the day in the Bright Angle Creek which flows from the falls near the North Kaibab trail down to the Colorado River or on the day we were at Indian Garden, we played cards under the trees.  It got to 110 deg at Bright Angle campground across from Phantom Ranch the day we were there.  I was also drinking in excess of 4-5 litters of water each day and adding salt to my food.  It was a really great hike but we researched and knew the conditions we were heading into and we heeded the warnings of the rangers and took lots of precautions which also included sun screen, hats, long sleeved shirts and soaks in the creek.  We hadn't wanted to go in June but it was when we could get permits.

I totally agree with @Dad_Aint_Hip , people are leaning too much on things like YouTube to get their information (I've personally backed out of a trip when the trip leader kept saying that this and that person said this or that on YouTube, and the trip leader was clueless and had never backpacked before and wouldn't listen to those of us who had as we were contradicting YouTube) and when inexperienced and excited, they don't think things through to realize they are only being told one side of the story.  Rangers and SAR can't hold their hands but I also think people think if anything goes wrong the Rangers and SAR will be there to save them so they don't have to take care of themselves.  I've heard those sorts of sentiments expressed while in our Parks.

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Found Myself Outside