Welcome to BYC and our state thread!
I'm not too far from you in the mayer area, my summers aren't as hot as yours, but my winters are a bit cooler. The guidelines, especially for size and ventilation, should probably be doubled. The minimums, withOUT doubling, are 10 sq ft run space per bird, 4 sq ft coop space, 1 sq ft ventilation above the birds while roosting, per bird, 1 ft roost space per bird.
For the weather, either get an app like weather underground, or look at any neighbors' flags to figure out the predominant wind directions. You'll need to orient your coop accordingly. Where I am, I seem to get the mildest if any winds from the east, and more severe winds from other directions.
Have you looked into a hoop coop? If you can get cattle panels (I think you have a tractor supply up there), this would be a great way to go. You can either use a lumber frame on the ground, or t-posts to hold the cattle panels. You can put a tarp over it, even wrap the tarp around the end to shield from the wind.
Oh, and predators---You may not have seen any of the various predators, but once you put the chicks outside, the predators will smell them and stop by.
Best of luck, hope you enjoy your chickens and your coop project!