It sounds like she is in the first stage of labor, a temperature drop is the first indication that she is getting ready. Though keep in mind some females can fluctuate as well.
Birth is pretty natural and most females know what to do, but we need to be ready in case mom has any problems. Some times the puppy's come though so fast that she is unable to get the sac off and the puppy clean before the next one. Other times it can be a hour between or more. To be prepare here are the things you are going to need.
1) Your whelping box this should be ready to go.
2) Old blankets, some old towels (I find cutting one towel into 4 or more squares is easier then using one towel because it will get messy. You need at least one square per puppy. A small sterile pair of scissors (This is to cut the umbilical cord if mom can not) Now I cut all the umbilical cords. Simply because mom tends to chew to low at times and can cause a umbilical hernia. Different breeders feel differently about it. You will also need gloves (Surgical ones) or you need to be very careful about keeping your hands clean. I suggest the gloves because it is quite messy and blood under the nails is messy to clean. I also like to have on hand some white flour. If the umbilical cord is bleeding apply a small amount between two fingers and gently squeeze the end of the cord. This will help with clotting and stop the bleeding. Some breeders use dental floss to tie off the cord. I prefer to stop the bleeding and go natural but you should have some on hand regardless in case the bleeding will not stop.
3) Water for mom
4) A good watch......write down the time of birth for each puppy as well as a small description of the pup The puppy's weight and length. Some breeders pick up small thin colored ribbons and place a different color ribbon on the lower back leg to tell them apart. Just make sure it is not tight as it will need to be adjusted as the pup grows.
Keep in mind that dogs tend to love to go into labor at night. So be prepared by keeping her near you so you can hear when she is ready. I myself set the alarm to go off every 3 hours so I can check on my dams when they are in the first stages of labor.
There are different things to look for in the first and second stage of labor in dogs. The first stage symptoms:
Dogs temperature will drop
She may be more clingy and want to be near you more
Her eyes may dilate some
May want to hide in dark places, or be by herself
Wants to lay on her side but can not get comfortable
The second stage of labor is a little easier to notice.
She may shiver, or shake some
She will pant or breath harder and faster
Digging at things such as the whelping box, bedding or floor
Looking at her rear end or licking the vulva more
The third stage is when the puppies are ready to come:
You will notice hard contractions. (Her stomach will get hard for a few minutes then go down)'
She may shake more or shiver more then before
You may notice her grunting, pushing or bearing down.
Not every dog will follow the above guidelines, but they are the most common. Once mom is in the third stage puppy's should come within a few hours. If mom is having hard contractions, pushing and trying to deliver but can not for more then 2-3 hours she has to see the vet. If more then 2 hours passes in between puppy's and mom is actively pushing then she must see the vet. (This is why writing down the time and using a watch is helpful). If a puppy becomes stuck in the canal you will need to take her in or try and free the puppy. You can do this by gently spreading apart the vagina and sliding one finger in to try and help push the puppy out. Do not grab or pull as you can kill the puppy.
Mom should immediately begin removing the sac.....if she has trouble (Keep in mind these can be tough to break) you can assist her with it by ripping the sac open. Allow her to clean the puppy as much as she can. If she stops and begins cleaning herself then you can pick up the puppy and clean it quickly. Rubbing gently is the key to help stimulate circulation and get the puppy dry. Weigh the puppy quickly and place it next to mom for feeding. Sometimes you have to help the little one latch on by moving the head and mouth over the nipple. Puppy's nursing will encourage contractions for mom.
Once all puppy's are born give mom a little time before any cleaning (less then a hour) then encourage her to come out for a drink or something to eat. I like to give chicken and rice with the dog food to encourage her to eat and give a good meal. Quickly clean the bedding and box at this time. Mom may come back curious, but as long as it is quite, and you are calm she should have no problem with that. Give her lots of praise during the labor and after so she knows you are happy with her. Most moms have no real problems with you picking up the puppy's for cleaning and such, but limit who is there to prevent stress.