Tonight 99.7.
The normal body temperature for dogs is between 101 and 102.5 F, compared to 97.6 to 99.6 F for humans.
When the temps drop to 98.0 or 97.8, it means within 12 hours labour should begin. You can get false drops but that doesn't stay down. So, when it drops like that, I usually check 10 minutes later. You must check 3 times a day or you will miss the drop.
There are other signs such as nesting that play a part in knowing it is time.
I won't be checking Leti's till the 10th.