"Some big dogs need jackets in colder weather, while others do not. Consider the temperature, your dog's fur thickness, and factors like weight and muscle mass to decide if your dog really needs to wear a jacket. Jackets can be helpful and effective for chill-prone dogs in colder weather. They can also be handy if your dog is reluctant to go outside when it's chilly."
"Large dogs can usually wear jackets for as long as they are comfortable in them. However, many experts recommend taking jackets off your dog after a maximum of 4-8 hours to avoid skin irritation, possible overheating and discomfort. Dogs should also not be allowed to sleep in jackets overnight, and they should always be watched when wearing them. Consider your dog's fur thickness and tolerance for cold when deciding how long to leave a jacket on him. Slimmer dogs and those with thinner coats may feel comfortable in jackets for hours at a time, especially if it is very chilly. Those with thicker coats and/or lots of mass may not need a jacket, or they may not need to wear one for as long. "