The Maremma Sheepdog has a double coat with long and lush hair on the top and a thick undercoat underneath. This was helpful to it when it spent long days and nights herding sheep in the European mountainous ranges. The coat protected them in all kinds of cold and inclement weather and even provided protection against brambles. It kept it warm and dry and was ideal for sleeping outdoors.
The same coat that did such a masterful job of protection in the cold mountain ranges can be a harder to bear in hot weather. The dog does not do well in hot weather and while an active dog, it will simply flop down in the shade and not move in hot weather. You can help it to control the heat by giving it plenty of water and leaving it in the shade. The fact that the coat is usually in lighter colors like white and tan also help to reflect much of the heat back into the atmosphere. The coat does not develop an odor, like other dogs, and cooling it down with water won't work that well. The coat is also water-repellant. Most owners don't need to bathe the dog since the coat simply be groomed and kept in shape without bathing. There is no odor to address either.
This dog does moult, but it is typically done at the start of winter. The bitches seem to moult more than the male dogs and they can shed their undercoat at the beginning of the summer. Otherwise, the dog's fur coat is pretty standard year-round. The only other time the dog might shed is if it is kept indoors and the central heating affects the season for shedding.
If you want to keep this dog's coat in good shape, you will need to brush it regularly. This won't help it to face hot weather, but it will help it reduce shedding during moulting season. The coat is a great for colder climates, but it can also be endured by the dog in hot weather. It naturally reflects heat off the dog, but the dog may decide to take it easy under a shady tree during the duration of the worst heat of the day.
A Maremma Sheepdog can be brought indoors if you are really worried about it expiring. It will be happy being indoors in a cooler area too. It may get a bit more active, if it feels better and you may have to deal with a little extra energy. These dogs are, however, outside dogs and will do just fine outside regardless of the weather. It may not be fun and it may stress the dog, but as long as they have shade and enough water, they should be able to survive the day.