A normal dog's body temperature is between 101 and 102.5 degrees Fahrenheit. Dogs are considered to have a fever at any temperature above 103 degrees Fahrenheit.
The only accurate method of determining a dog's temperature is by using a rectal thermometer. Symptoms of fever in dogs are lethargy, loss of appetite, vomiting and a depressed mood. The most common causes of fever in dogs are infection and consuming toxic substances. Vaccinations may also cause a low-grade fever. An elevated temperature due to hot conditions or excessive exercise in such conditions is called hyperthermia. This condition may be fatal if the dog's temperature rises above 106 degrees Fahrenheit.