How do they do in Summer heat. It gets pretty hot and humid where I live. A friend is thinking about getting a couple of GP pups and raising them along with a few Alpaca. The idea being the GP's will guard the livestock.
We have about 4 months of brutally hot weather here.
In NC it's 90 degrees+ for 3 months and frankly our pyr is a house pet rather than a guardian, so she spends a lot of time indoors, sleeping, hanging out. She's 16 months old and just chills out all day. So ours doesn't spend tons of time outdoors. Most of her exercise consists of long walks and/or the dog park down the street, but they are a pretty low-energy breed to begin with.
With that said, she absolutely prefers winter over summer. I think she handles it just fine, but it's pretty obvious that she has a preference. Also, you're not supposed to shave them due to the double coat, it acts as insulation.
It's hard for me to say exactly how she'd fare in your situation, but there are a number of social media groups for these dogs and I'd absolutely suggest you join one and ask some questions of other folks who actually use their GP as a working dog. They are definitely good working dogs as well, we just didn't raise her that way.
She is the best dog I've ever had in my life and I would absolutely get another one.