Question for BBT experts :)

I have been chatting for 3 months now. I am pretty good with taking my temp at the same time every day. Saturday I had a HUGE drop. I live in an apartment and it was a lot hotter than usual the night before last so we slept with a fan blowing directly on us. ( we can't control the heat in our unit :( ) I also had to wake up a lot earlier than usual for work. I usually wake up about 9:45 am and temp. Saturday morning I had to wake up at 7am. My Temps the last few days were:

97.84, 97.86, 96.75 ( that was saturday) 97.56, and 97.53 (today). I got my peak opk this morning. I have never had such a huge drop like this. Is this normal because I took my temp much earlier and because of the fan or could my body just have had a huge pre O dip? Just wondering g of I should ignore this low temp. I am using fertility friend to chart. Any help would be apprecisted. THANK YOU!