The temperature minimum is the lowest point of core body temperature within a 24-hour cycle. This nadir typically occurs just before the body prepares to wake ¹. Because core body temperature is tightly regulated by the circadian rhythm, the timing of this minimum provides a reliable indicator/anchor point/reference point of an individual’s internal biological night.

Understanding your temperature minimum is crucial for anyone seeking to adjust their sleep schedule or recover from jet lag.

Suppose you usually wake up at 7:00 AM. Your temperature minimum likely occurs between 5:00 and 5:30 AM. If you want to shift your sleep schedule earlier, you would seek bright light exposure after this time. Conversely, to shift later, you would expose yourself to light before this minimum.

To estimate your temperature minimum, record your core body temperature immediately upon waking for 3–5 consecutive days. Average these readings to approximate the nadir.