Seasonal Changes in BBT?

I’m semi new to BBT. I started in August and quickly got pregnant. Unfortunately we suffered a mc. My BBT was always in the 97 degree range besides when I ovulated it was pregnant at 98. I’m wondering if someone who is experienced with tracking BBT can let me know if it’s normal to see temp changes based on the season. I have had some high 96 degree ranges this winter. So since it’s been colder has and one else had a lower temperature or what could be the cause?