What breed is he?Is it cold in the house?How is he acting?Is he eating, drinking, urinating and defecating normally?
Any vomiting or diarrhea?
I'm getting ready to log off for the evening, but didn't want to leave you hanging with no answer.
Dogs can feel cold to the touch for several reasons, with the most obvious one being that they are, indeed, cold. If your dog is short haired and your house is chilly, then that's likely the cause of the being cold to the touch. Turning up the heat may help, or you an purchase a little dog sweater for her at your local pet store. Depending on your dogs size, you may even be able to find something in the children's department at your local big box store. I have a 14 year old lab mix who wears a boy's hoodie sweatshirt that I bought at Walmart.
If the cause isn't that she's cold, there could be something more going on. Issues like anemia (low iron in the body) or shock (usually after some kind of trauma) or even some organ dysfunctions can cause the dog to be cold to the touch.
The best thing to do at this point is to take her temperature. You can use either a digital or a manual thermometer. Use some sort of lubricant (even kitchen oils or dish soap can be used in small amounts) and once it's lubricated, insert it into her rectum about an inch deep. (Most dogs do not appreciate this intrusion, so you may need a second person to hold her for you. A demonstration of the method of restraint for this kind of procedure can be found here: http://www.youtube.com/watch?v=z6nHOKQ216k (if you're using a digital, leave it in place until the reading tells you to remove it) If you're using a manual thermometer, leave it in place for between 60-90 seconds to ensure an accurate reading. The normal temperature for a dog is between 101 - 102.5. If your dog's temperature is lower than 99 degrees, then there's something going on internally that will need to be addressed by a vet immediately. Hypothermia (being too cold) can be fatal if left untreated, so start with taking her temp and go from there.
If her temperature is within normal limits, you can simply keep her comfortable and warm as best as you can tonight and then give your vet a call in the morning..just to be on the safe side.
I hope this helps.