The temperature that large dogs overheat is between the temperatures of 81 F to 85 F degrees.
A dogs normal body temperature is 101.5 F and overheating occurs when the dogs body temperature rises only a couple degrees above 102 degrees F.
It's important to take action before the dog suffers heat exhaustion as the dogs body temperature can rise to dangerous levels very quickly.
If the dog's body temperature is 104 F they are certainly overheating which can be dangerous to the dog if not brought down quickly enough.
The temperature at which small dogs overheat is when the small dogs body temperature rises over 102 F degrees.
Small dogs can overheat easily even when the outdoor temperature or indoor temperature is 80 F or above.
The dogs body temperature can rise even when the temperature is only 80 F to 90 F and they can begin to feel hotter and can easily overheat.
This is especially true when a dog is left in a car or vehicle where the outdoor temperature is only 75 F to 80 F degrees.
The inside of the car or other vehicle can reach higher temperatures than the outdoor temperatures and it can easily get to 100 F or higher inside the vehicle even though the outdoor temperature is only 80 F to 85 F degrees.
This is why even in slightly cooler temperatures that may feel just warm outside you should never leave a dog or child inside the vehicle as they can easily overheat.
Any temperature above 85 F is considered too hot or too warm for a dog to be left in longer than 4 hours.
If the temperature rises above 85 F for any length of time the dog should be in a cooler environment to avoid them overheating.
Also make sure the dog has plenty of water to drink.