What is the highest temperature my cat can be kept out in?

Question: 

My 3 large cats; >15 pounds each are in an enclosure 4' high, 4' wide' and 10' long, with covered shade and boxes, food and water. What is the highest temperature that they can be kept out in? I live in Phoenix, Arizona.

Answer: 

Animals are more susceptible to heat stroke than humans, given they cannot sweat to cool themselves. A large, well furred cat will overheat faster than a person. We generally recommend bringing pets indoors in a cool area when the outdoor temperature is higher than 85 degrees Fahrenheit. If this is your cats’ primary living area, additional enclosure length and height is recommended, as cats need climbing and exercise areas for appropriate quality of life, and additional space will also offer increased airflow. If this is simply an outdoor play area, and your cats are able to come inside during warmer weather, the enclosure is suitable. Your veterinarian can evaluate your cats’ habitat and assist you with environmental accommodations.