Dogs have fevers when their body temperatures meet or exceed 103 degrees Fahrenheit, notes WebMD. A fever that is 106 degrees Fahrenheit or higher is considered life threatening. Fevers are diagnosed by taking dogs' temperatures with a rectal thermometer. Dog owners may notice other possible signs of fevers, which can include vomiting, diminished appetite, coughing and shivering.
A dry nose is not necessarily a sign of a fever, according to WebMD. Conversely, a cold wet nose does not indicate that a dog is well. Dogs can also have high body temperature due to external factors, such as running in very hot weather. This type of high body temperature is called heat stroke or hyperthermia.
According to PetMD, a fever is indicative of a larger health problem. Therefore, a dog with a fever should be taken to the veterinarian for diagnosis. Common triggers for fevers in dogs include infections from bacteria, parasites and viruses; tumors; endocrine diseases; certain inflammatory conditions; cancer; reactions to certain toxins; and metabolic diseases. Sometimes the origin of a fever is never determined.
WebMD notes that a dog may also have a low fever after receiving vaccinations or while taking certain medications prescribed by a veterinarian. These fevers typically last between 24 to 48 hours.