No breed should be left in the heat. Breeds that are prone to heat stroke are Pugs and really any breed with a pug type snout (short snout). Other examples other than Pugs are Shih Tzu’s, Tibetan Spaniels, Pekinese, etc. These breeds can't handle it. Sylvia, my black Pug, and Morty, my Tibetan Spaniel mix, can only be outside in the summer for 5-10 minutes at a time unless they are in the pool. Not having the air conditioning on in hot weather is not an option in my house.