My dog's coat is very thin all year long. She is an indoor dog, so I don't think the seasons have a great effect on her coat.
However, back in the 1980's when we had several dogs that lived outside on chains in dog houses, I recall that their coats did get very thick in the winter. To get the excess hair off, I used to give my dog a rub down after every walk, starting on the hind legs, then the front legs, then the body and lastly the muzzle and ears. It is important to always rub with the lay of the hair and not against it. It is amazing how much hair will come off using this method, not to mention the comfort the dog feels after a long walk or run. I hope this is of some help.