If you believe your dog has a true fever, you should seek veterinary attention. Virtually all causes of fevers will require veterinary treatment. While you need not rush to an emergency clinic in most cases, you should try to get in to see your vet within 12-24 hours.
Never use over the counter medications like Tylenol or Advil to treat your dog’s fever. Not only will this fail to address the underlying cause, it could make things worse by causing gastrointestinal upset as well as liver or kidney damage. Unlike dogs who are just overheated, it is not helpful to actively cool a dog with a fever.
On the other hand, if you believe your dog is hyperthermic (overheated) you should definitely get them into a cool environment and offer them cold water to drink. Pointing a fan at them, and applying cool packs in their armpit and groin areas can also help.
Avoid using ice cold water or cold packs — cool is better than cold in these cases. All that being said, if their signs of hyperthermia are moderate to severe (anything more than heavy panting) you should head to your nearest emergency clinic ASAP. For example, if you are dealing with a dog who was left in a hot car or outside during a heatwave with no access to shade or water. Heat stroke is a life-threatening condition in dogs.