Protecting dogs in winter from extreme cold, ice, salt and deicers
Dogs are just like people in that they have varying tolerance for different temperatures and ground conditions. Some dogs can run around in the snow for hours, and they actually end up panting—their version of sweating—from all the activity. Others start shivering and pulling at the leash to go back indoors after being outside for only a few minutes.
There's really no cut-off temperature for it being too chilly to take your dog outside. However, you should always watch your pet carefully for cues that it's too cold and act accordingly—some pets benefit from a jacket and even snow booties.
Never leave your dog alone in the cold or inclement weather, as he could develop hypothermia, a veterinary emergency.
You don't need to stress too much about protecting your dog's paws from salt and chemical deicers. If he were to eat a bag of these products, yes, that would cause real trouble and warrant a trip to the veterinary ER. But if your dog licks a little off the bottoms of his paws, he will (at worst) experience an upset stomach. You can avoid this by wiping off his paw pads with a damp washcloth after each walk.
Some dogs do tend to collect ice and snow between their toes. Signs of that include prancing in place, shifting weight from one foot to another, and biting at the cold bits between their toes. There are lots of products available to help repel water and keep paws comfortable. Vaseline is nontoxic and safe to use, though I recommend wiping it off afterward as it can cause minor stomach upset (my own dog accidentally ate an entire jar of it recently and had terrible diarrhea for days).
Every veterinarian will agree that tired dogs are good dogs. So unless your pet is so small that it can adequately exercise in your house, going outdoors is essential. Exercise stimulates dogs mentally and provides bonding opportunities with their owners, while getting out excess energy and providing numerous health benefits, just as it does in people. While we may want to hibernate in winter, it's important to stay as active as possible with your dog.