A study by Waterhouse et al. (2012) provides a clear example of the body's circadian temperature rhythm, illustrated by a line graph. The data shows that over a 24-hour cycle, body temperature is lowest during the early morning hours of sleep. It drops from approximately 98.8°F at midnight to a low of about 97.6°F around 4:00 A.M. The temperature then begins to rise, returning to its initial level by 8:00 A.M. and continuing to fluctuate at a higher level throughout the waking hours before declining again with the onset of the next sleep period.