Many people seem to think that because Labrador Retrievers are short-haired that they don’t shed. Anyone who owns a Labrador Retriever will of course tell you that they shed quite profusely at times. Labs have a double coat, which means they have a water-proof outer coat to protect them when they’re swimming, and a softer, more downy, under-coat that protects them when swimming in very cold water. 

Labradors tend to shed more thoroughly when one of two things happen. Often, Labradors shed more excessively when they are 5 or 6 months old, and undergo their first major shedding, in which the "puppy coat" is replaced by the adult coat. Secondly, many Labradors respond to a change in season with a thorough shedding. It would seem that in your case, both reasons may be affecting your Labrador. Your Labrador will continue to shed in stages throughout his life and, particularly if he is sensitive to seasons, each subsequent shedding may be no less severe.

There is nothing you can do to reduce the amount of shedding, but you can make it more manageable by wet grooming him several times a week in a warm bath. Heavily massage the coat with a rubber grooming brush or mitt when the hair is wet, thereby removing loose and loosening hairs when it suits you.