Question about O and the thermal shift

[Sahara]

OK, so you O first, then see the shift, right? I have all of the fertile signs the first day of the thermal shift, which is usually only about .3 degrees, then the second day I have another shift that is about .3 degrees. On the second day, I wake up with all the fertile signs, and then by the end of the day they are gone. It happens so fast, within 12 hours, is that normal? When's the best time to BD, the first day of thermal shift, or the morning of the second day? (Well both obviously)

[Arduinna]

It's best to bd before the temp shift, but the first day of temp rise is also a good day to bd. But before the temp rise is the best.

The drying up of cm is also a good sign of O. You also could just bd as long as there is fertile mucus.