When I started flying I deliberately waited until the midst of winter to ensure that I would get my PPL(A) while there was still a bit of summer left .. lo and behold, it worked! Took me six months from start to finish. Most of the flying between april and july, obviously.
That being said, it wasn't that hard finding flyable weather during winter. My logbook tells that I got 21 hours in january-march. That's nearly half the course (or about a third if you're like me and a slow learner
) and in any case, very far from being "down-time".