When interpreting temperatures, you’ll want to train your eyes to “see the forest through the trees.” The key to doing so is to look for a pattern of lows and highs. In other words, you’ll find that your temperatures before ovulation will go up and down in a low range, and the temperatures after ovulation will go up and down in a high range. The trick is to see the whole, and not focus so much on the day-to-day changes.

I learned how helpful this concept is when I first taught at a women’s clinic. Within a few weeks of the first class, I would inevitably start getting calls from clients who were convinced they must not be ovulating. But when they read me their temperatures over the phone (back in the Paleolithic Era, before email), the pattern seemed perfectly evident. I couldn’t understand why they didn’t see what I saw. Then it dawned on me. They were not seeing the pattern, but were instead focusing on the fact that on Monday it was up, on Tuesday it was down, on Wednesday is was back up, and so on. Remember, stand back and see the whole picture.

The preovulatory temperatures are suppressed by estrogen, whereas the postovulatory temperatures are increased by heat-inducing progesterone. In fact, one of the ways to remember that the second phase of the cycle is the “progesterone” phase is to think of it as the “pro-gestation” phase. In other words, this is the phase of the cycle that is warmer, as if designed to act as a human incubator to nurture an egg which may have just been fertilized.

I want to stress here that the rise in waking temperature almost always indicates that ovulation has already occurred. It does not reveal impending ovulation, as does cervical fluid and cervical position. In addition, you should also be aware that in only a minority of cycles will women ovulate at the lowest point of their temperature chart. Because a preovulatory temperature dip is so rare, women should not rely on its occurrence for fertility purposes. Rather, they should use the cervical fluid and cervical position to anticipate approaching ovulation.