I live in the high desert of Central Oregon. Our hot spots don't get to 120, but over 100 is definitely common.
Without water, without adding mulch and soil, and without putting up shade structures, I'm afraid there's probably not much you can do. I'm not trying to be negative here, but it's an extreme environment that we live in and it takes money and resources to change.
My suggestion would be to buy one piece of lumber at a time and eventually put up a pergola. Save your pennies and buy a rain catch system for the hot spot, one piece at a time.
Trust me, I feel your pain. When I moved to this Godforsaken place from Pittsburgh, PA, I verbally cursed it every single day (without fail) for a year. You can't compost here without a whole lot of effort.
It's too hot during the day and then it's too cold at night. If a plant can tolerate the 95-degree heat during the day, then it probably can't tolerate the 35-degree temperature that the night brings. And even if it can tolerate both the heat and the cold, it probably can't tolerate the drastic temperature swing. *sigh* But, I love my husband, so in the high desert I stay. LOL!
Extreme environments require extreme measures.