Too big of a dip before ovulation?

Hi!

This morning, my bbt drop quite low. I’m on CD13. Does this mean that I will probably ovulate today or tomorrow? I’m a bit sceptical of that big of a dip. Is it possible to drop that low before ovulation? (I didn’t think to take my temperature a second time this morning to make sure it was accurate…) At least I know that it can’t be my period coming as it is way too early (usually I have 28 to 30 days cycles.) Here is my chart.

What do you think?

Thank you