What should an adult's temperature be?

Body temperature ought to be 98.6º Fahrenheit / 37º Centigrade

The average oral temperature of human adults is usually thought to be and often shown on thermometers as 98.6 degrees Fahrenheit. But this value was determined in the 1800s and modern studies have shown it to be 98.2° ± 0.7°F. A wide range of temperatures has been found in healthy people. My average temperature is 97.3 F which is below that range. Also, people's temperature varies about one degree through the day (24 hours).