In that climate a dog needs shade throughout the day. You can make a shade directly over the dog's area by using the same material that plant nurseries use to set up shaded areas for their shade-loving plants.
I'd also want my dog to have a shelter that was elevated off the ground so that air circulated underneath, and it wouldn't hurt to have a roof that had some ventilation under the eaves to let the hot air escape.
Any kind of enclosed house - like an igloo - is going to accumulate the dog's own body heat since there is no way for it to escape. If you stop and think about the climate where humans build igloos to live in, using one to escape hot weather just doesn't make any sense.
Most dogs who spend time outdoors in the summer usually appreciate a child's wading pool full of water, too, and it's great fun to watch them play and cavort and just generally enjoy the water.