Grooming expert Diana North advises:

Grooming your dog’s coat is important at any time of the year, in particular when the coat is changing in spring time. Winter coats tend to be thicker and longer and in bad weather the coat collects more dirt and debris so will take more time to comb. Perhaps this is what is meant by grooming more often. Good grooming throughout winter will help when spring arrives and the new coat is coming through — if you have not kept the coat free of dead undercoat and knots then you will have a mixture of dead and new coat, making it very difficult to get through the coat with your brush or comb.