Temporal temperature is a body temperature reading taken from the temporal artery, a blood vessel that runs across the forehead just beneath the skin. A temporal reading of 100.4°F (38°C) or higher is considered a fever. This method has become one of the most common ways to check for fever at home and in clinical settings because it’s fast, noninvasive, and reasonably accurate.
Why the Temporal Artery Works
Your body has dozens of arteries near the skin’s surface, but most of them have built-in valves that adjust blood flow depending on conditions like air temperature or physical activity. The superficial temporal artery is unusual: it lacks these valves, which means blood flow through it stays essentially constant. That consistency is what makes it a reliable spot for estimating core body temperature, the internal temperature that matters medically.
The goal of temporal thermometry is to get the convenience of a skin-level measurement with accuracy closer to what you’d get from an invasive method like a rectal thermometer. The thermometer’s internal software uses algorithms to calculate core temperature based on the heat radiating from the artery, compensating for the fact that skin is naturally cooler than your insides.
How Accurate It Is
Temporal readings tend to run slightly lower than rectal readings, which remain the clinical gold standard for precision. In a study of children presenting to an emergency department, temporal artery temperatures averaged 0.2°C (about 0.36°F) lower than rectal temperatures overall. The gap was small in children without fever, just 0.05°C on average. But in children who did have a fever, the difference widened to more than 0.5°C, meaning a temporal scanner can underestimate a true fever by nearly a full degree Fahrenheit.
This matters most at the boundary. If your child’s temporal reading is 99.8°F, it’s possible the actual core temperature is already at or above the 100.4°F fever threshold. For routine monitoring at home, temporal thermometers are practical and useful. But if a reading is borderline and you’re concerned, a rectal temperature in infants and young children gives a more definitive answer.
What Counts as a Fever
The Mayo Clinic uses the same fever cutoff for temporal artery readings as for rectal and ear thermometers: 100.4°F (38°C) or higher. Normal body temperature hovers around 98.6°F (37°C), though healthy readings can range from roughly 97°F to 99°F depending on time of day, activity level, and individual variation. Temperatures tend to be lowest in the early morning and highest in the late afternoon.
How to Take a Temporal Reading Correctly
Technique matters more than most people realize. The temporal artery runs horizontally across the forehead, so you scan straight across, not downward. Curving down toward the eyebrow will miss the artery entirely and give you an inaccurate number.
Here’s the proper method: press and hold the scan button, then gently slide the thermometer in a straight line across the forehead from one side to the other. Keep the probe lightly touching the skin. The whole process takes about three seconds. If you want to take a second reading for confirmation, wait roughly 30 seconds between scans so the skin can recover from the slight cooling effect of the probe.
For infants, you can get an accurate reading with just a gentle two-inch touch across the temporal artery area. Pressing the scan button before touching the baby’s head helps avoid startling them.
What Can Throw Off a Reading
Because temporal thermometers measure infrared heat from the skin’s surface, several external factors can interfere with accuracy:
- Sweat or perspiration on the forehead cools the skin through evaporation, which can produce a falsely low reading. This is particularly relevant during a fever, since fevers often cause sweating.
- Ambient temperature and humidity affect skin temperature. Taking a reading immediately after coming in from cold weather, or in a very hot room, can skew results.
- Physical activity or exercise increases blood flow to the skin and raises surface temperature, potentially inflating the number.
- Hair covering the forehead blocks the thermometer’s sensor. Brush hair aside so the probe makes clean contact with skin.
- Inconsistent probe distance matters for non-contact models. Hold the thermometer the same distance from the skin each time, following the manufacturer’s instructions.
For the most reliable reading, take the temperature when you or your child have been resting indoors for at least a few minutes, with a dry forehead and no hair in the way.
Temporal vs. Other Thermometer Types
Rectal thermometers remain the most accurate method, especially for infants under three months, because they measure temperature inside the body rather than estimating it from the surface. Oral thermometers are also reasonably accurate but can be thrown off by recent eating, drinking, or smoking. Ear thermometers work well when positioned correctly, though earwax buildup can block the sensor and cause errors.
Temporal scanners fill a practical middle ground. They’re faster than oral or rectal methods, less invasive, and work on sleeping children without waking them. Their main limitation is the tendency to read slightly low during actual fevers, which is worth keeping in mind when a reading sits close to the 100.4°F threshold.