charting temperatures

I had my Ovidrel shot last week (Thursday, Dec 10), IUI Dec 11 and Dec 12. I hadn't ovulated either of those times but on the 12th, the RE said I looked really close.

My temperature finally went up this morning, some 108 hours later.

Google results showed that only 60% of women have a temperature increase exactly the day after whereas the remaining 40% have it a few days later.

Is it that or is it that I ovulated late? Is this even possible on Ovidrel? I had thought you were supposed to ovulate 36-50 hours after Ovidrel?

This happened last month as well.