Radio picked up distant station on same frequency?

I was driving in my car today listening to a local radio station 89.7, which is from eastern Pennsylvania where I live. As I got off the highway, the music changed, and I was listening to a different station... from Cape Breton! A quick search online shows that that station is also 89.7, but very far away. For about a mile, the stations were back and forth eventually returning to normal. What could cause this?