Are worms as much of a problem in northern areas?

I'm in Vermont and have my first flock of 16 chickens. They're about 5 months old. I was just reading a thread about worms. It seems like most of the posts are from people on southern states. Are worms as much of a problem up north? The first feed we gave them was medicated, but other than that we really want to keep these chickens as natural/organic as possible. From what I was just reading it sounded like the natural methods don't work so well.