Is hair loss on a short-haired puppy normal?

I have a small Manchester Terrier (essentially a miniature pincher) that is about 10 months old. Recently, I’ve noticed her hair thinning around her ears, top of her head, and legs. We live in a cold climate. Is this normal for a dog of her type / age? Is it seasonal? I’ve heard that short-haired dogs occasionally have I “thin” period when beginning to grow their adult coat… Is that so?