The coverline is drawn after your basal body temperature has risen because of ovulation and stayed up for at least 2-3 days. Q: Are there any basal body temperatures that I should ignore when drawing a coverline?
A: The coverline is drawn after your temperature has risen because of ovulation and stayed up for at least 2-3 days.
This is called a "sustained" elevation and indicates that ovulation has taken place.
It is possible that prior to the rise, prior to ovulation, the temperature may have dropped for a day below what eventually will be the coverline. That one-day temperature should be ignored in order to create the coverline.