Your basal body temperature (BBT) usually rises within about 0–2 days after ovulation, but the exact timing can vary from person to person and even cycle to cycle.

How soon after ovulation does BBT rise?

Most expert and medical sources describe the BBT rise as happening shortly after ovulation, not before it. Progesterone released by the corpus luteum after the egg is released causes a small “thermal shift” of roughly 0.3–0.5 °C (about 0.5–1.0 °F).

In practical charting terms:

  • Many people see their BBT rise the day after ovulation.
  • For others, the clear sustained rise doesn’t show until 1–2 days later.
  • Research and real‑life charts show that only a minority get a textbook “rise the very next morning” every time; sometimes the shift is slower or more subtle over several days.

So if you’re looking at a chart, the “ovulation day” is typically the last low temp before a sustained rise , rather than the day the temperature goes up.

What the pattern usually looks like

After ovulation:

  • BBT climbs by about 0.4–0.9 °F (0.2–0.5 °C) compared with your follicular‑phase temps.
  • It then stays consistently higher through the luteal phase until just before your period, when it usually drops again.
  • If pregnancy occurs, the higher temps tend to stay up beyond the usual luteal length (often 14+ days after ovulation).

A simple example: if your pre‑ovulation temps hover around 97.4 °F, your post‑ovulation temps might cluster around 97.9–98.3 °F and stay there until either your period or a positive test.

Things that can confuse the timing

Your BBT pattern can be delayed or blurred by:

  • Irregular sleep or taking your temperature at different times.
  • Illness, fever, alcohol, stress, or travel.
  • Using a different thermometer or switching oral/vaginal/rectal measurement methods mid‑cycle.

These can make it seem like the rise is “late” or inconsistent when it’s really the data that’s noisy.

Key takeaway

For most people, BBT starts to rise immediately to about 2 days after ovulation , with a small but sustained jump that marks the beginning of the luteal phase. You can’t reliably predict ovulation before it happens from BBT alone, but you can confirm that it likely already occurred once you’ve seen several days of higher temps in a row.

TL;DR: BBT does not rise before ovulation; it usually goes up within 0–2 days after and then stays higher for the rest of the cycle.

Information gathered from public forums or data available on the internet and portrayed here.