The normal body temperature for a dog falls within the range of 100°F to 102.5°F (about 38°C to 39.2°C).
If your dog's temperature is outside of this range, you should contact your veterinarian. Body temperature over 104°F or under 99°F indicates an emergency situation.
In general, the most accurate way to measure a dog's body temperature is rectally. However, some ear thermometers made especially for dog's ears can be considered somewhat accurate. In a pinch, temperature can be measured in the axillary region (underarm) and one degree can be added to the final reading. Be aware that this measurement is approximate and NOT considered very reliable. It is also important to understand that you cannot gauge a dog's body temperature by touch. In addition, a warm or dry nose does not necessarily indicate a fever or any other health problem.