We have so much natural shelter here it is hard to answer from my own experience. I do have dog houses in most pastures here at home just to keep the AR people happy, and the dogs never use them. Quite probably it was the thunder that sent the dog to your back porch...many of these LGDs are not very fond of loud noises. So shelter might not have helped there. Very few of my dogs ever seek shelter from rain (the one or two that do, go under my stock trailer). From the perspective of dog health, probably the most important consideration is that your dog be able to stay cool in the summer heat. I find water is the most beneficial way to cool a dog. I make sure my pups know they can cool off in the stock tank. Shade is also very beneficial. Most of my dogs just hop out over the fence to find some shade, but if your dog cannot do this, you need to be sure it is provided within the paddock.
Tamarack Prolific and Ile de France crosses