Use ovulation testing for ovulation prediction and BBT temping to confirm ovulation. LH begins to rise over the course of a few days and finally surges drastically 24-36 hours before you actually ovulate. This is what makes this hormone a good indicator that ovulation is about to occur and allows you to time intercourse accordingly. BBT rises after ovulation, due to increased progesterone released from the corpus luteum after ovulation. An increase of 0.5-1ºF indicates the BBT spike and occurs one-to-two days after ovulation.