The coverline is a horizontal line drawn after ovulation to help differentiate temperatures before ovulation (low) and temperatures after ovulation (high).
Your BBT or Basal Body Temperature is your body's temperature at rest, when you have slept for several hours. The best time to take your BBT is first thing in the morning when you wake up, before you get out of bed.
Your temperature may go up and stay up above the coverline for 14-16 days after ovulation. That is called a "biphasic curve".
The coverline is a horizontal line drawn in your basal body temperature
BBT chart after ovulation has been established. It is drawn just above
the last temperature prior to the first rise in temperature.
How is a visual interpretation of ovulation and coverline done?
A fallback temperature happens when your basal body temperature that was above the coverline drops for 1-2 days below the coverline.
Learn how to chart your basal body temperature (BBT)
The coverline is drawn after your basal body temperature has risen because of ovulation and stayed up for at least 2-3 days.
How to draw a coverline when fertility charting.
When your waking body temperature rises more than 0.2 or two-tenths of a degree higher than the previous six days, and it stays that way for at least two days, you can start drawing your coverline.
How do I determine my coverline?