What temperature is too cold for labradore dogs?

In general, dogs can tolerate colder temperatures as long as they are well fed, healthy, and protected from wind and wet weather. Some dogs absolutely thrive on cold weather. You don't say under what conditions you mean--are you talking about leaving them outside all winter, day and night, or just for short periods so they can get some fresh air and exercise? Labs are active sporting dogs that usually do well hunting and being outdoors in all kinds of weather. However, they should always have access to food, water (make sure it doesn't freeze) and shelter--a sturdy wooden doghouse raised off the ground, not too big but just large enough for the dog to stand and turn around (if it is much bigger, it will not hold in the dog's body heat and the cold air will circulate), with a door opening that has a flap to keep out the wind. Even better is a doghouse designed with the door opening off center down at one end so that the opening does not lead directly to the area where your dog will sleep, thus keeping drafts out. Blankets will get wet and freeze and not provide much warmth, your dog is better off with a generous amount of clean straw that is replaced regularly (not HAY). If possible, you can also provide a small lamp for the purpose of heating the doghouse, although you want to be absolutely certain it is installed away from where your dog can chew it (perhaps run the wiring through a pipe) or any of the bedding can catch fire. If nighttime temps dip below freezing, I would say to bring the dog inside.