Newfies are adorable, sweet dogs, but I would worry about how comfortable a dog like that would be in the SD climate. Most Newfies I have encountered lived in the snow or in places where it doesn’t get that warm like Seattle. I have a friend in Oceanside with a wolf-hybrid that has long, thick hair like an Alaskan Malamute, and she (the dog, not the friend) seems to suffer a bit, even on the coast.
But Newfies are amazing, gentle dogs! I used to work at a ski resort in Tahoe where the owners had one named Cosby. Cosby would hang around the lodge looking for toddlers with cookies or a hotdogs in their hands–then you would see the toddler’s ENTIRE ARM disappear into the dog’s mouth. Just as quickly the arm would come out, absent the cookie or hot dog. Kids never knew what hit them.