There's an old saying: a dog can take a ton of cold but only an ounce of heat. That's true, but too much cold can still cause your dog considerable discomfort, and in extreme cases, even death.
Hypothermia is perhaps the most dangerous cold-weather ailment a dog will ever face. Even tough, cold-weather animals like Labs and Chesapeakes can fall prey to hypothermia. Signs are extreme shivering, seeming disoriented and continually trying to nest by burrowing into the grass or brush.
Hypothermia is a danger primarily when a dog is cold and wet. Cold, dry weather alone is rarely enough to trigger a hypothermic reaction, especially if the dog is running. But add water, either in the form of rain, a river the dog has plunged into or something similar, and a dog can get hypothermic in a hurry.
If you suspect your dog is getting hypothermic, warm him up any way you can. Towel him dry, put him under the heater of your car, but get him out of the elements. When treated quickly, most dogs recover with no problems, but it never hurts to have a vet check-up post hunt.
For retrievers and pointing breeds alike that will be exposed to cold, wet conditions, a great preventative is a neoprene dog vest. Even thin-coated dogs can handle cold weather wearing a neoprene vest.
Another common problem is ice balls that gather between a dog's feet. There's no way to completely cure the problem, but short-haired breeds are much less susceptible to it. On long-haired breeds, trimming the hair between their toes will help a little, but won't eliminate it.
The only real preventative is to boot your dog. There are dozens of styles of dog boots to choose from.
Finally, dogs that hunt in cold weather need increased calories to keep them warm, so you can up their food intake by as much as 50 percent, depending upon how much they're working. It's best to feed them after the hunt, not before it, however.
Also, make sure they drink water while they're exercising. In cold weather, a hard-working dog can easily dehydrate, so carry water with you and make him take a drink from time to time. He may not act thirsty, but he'll run better and last longer if he's properly hydrated.