
I find the temperature checking 100% accurate for me personally. I have heard the odd people say their dog objects to it or they don't like doing it but mine will let me do anything to them so it never stresses them out.
The book of the bitch if I remember words it a bit strange. It says somewhere along the lines of it can drop to 99 but then in the next sentence it says it can drop even lower. Can't remember exactly how it is worded but when you keep reading it does say it can go lower.
Generally the temp sits aroung 99.8- 100 Degrees F whilst pregnant, then drops over a period and can fluctuate up and down but once it goes down and stays down for a good 12 hours down nearer 98 then this is generally a good sign things are about to happen.
A lot of people dismiss the temp signs or say they never noticed the peak or their bitch never had a temp change , but taking it at regular intervals and charting you will honestly see it and it has always been spot on for me. I personally believe the temp drop is the body getting the pups ready for the outside world.
My very first litter was 1 week early. I checked her temp and it was down near 98 , I rechecked a couple hours later.I was honestly questioning it , with it be so early and she was showing no other signs still eating just a bit quieter. I decided not to let her out my sight, I had a quick jump in the shower and out I came.. there was a pup on it's way out.
Since then I have charted it on a note pad from the last week and been spot on everytime. Some dogs show so many external symptoms making is so easy to tell others don't.
I don't say this to worry you but a temperature temp that has been low for too long is also a possible warning sign of Inertia which requires assistance. The cervix can be open but no contractions.
Good luck