On the PCT a 20 mile distance between water sources is really just a day hike.
Many of those long stretches are broken up by water caches, and while they say not to depend on them (and really, you can get by without depending on them), I can’t recall any of the caches being empty when I went by. In fact, I was annoyed sometimes there were so many bottles along the way.
There is a 35 mile stretch that is bound on both ends by large caches. Even if those caches had not been there, the reality was that there was a water source in the middle of that stretch. It would have required a 2 mile detour (or a reroute, which is what I had planned for myself if the first cache had not been there.) Often this is the case with the long stretches. The long stretches have places to get water but they require a significant detour from the trail. In other words, you aren’t going to die. There is water. It just isn’t convenient.
I do have to admit that by Kennedy Meadows drinking from cattle troughs was starting to get from me. But the positive that I got from the experience is a reverent feeling of gratitude for water and the life it provides.
It can get quite hot in some places, but it’s a dry heat so quite bearable. Hottest day I experienced was along Deep Creek. Around 103. But there was water every so often and I would soak my shirt and hat and was fine. The hot days you will experience in So Cal are always cooled off each evening. It’s really not that bad.
In northern California I experienced a lot of hot days with hot nights, too. Thank goodness for trees to provide shade.
As for wilderness, you will see some of the world’s most beautiful and famous wilderness places. The mountains are BIG and stunning. With the burn zones, you’ll be witness to the cycle of life. Fire is part of nature, especially out west. The chaparral, which most people disparagingly call the desert, is a biotic community rich with life. You’ll see more wildlife in So Cal than you expect. Wildflowers in the desert inspire rapturous feelings of springtime, too.
Enjoy your hike!
Piper