Unknown Sound - Minnesota -

I woke up at 6:15 am to let out the dog, she wouldn't go outside, so I stepped outside with her because she normally goes out without a problem. When I stepped outside there was this loud roaring noise that didn't stop for two hours! It scared me.This is nothing like I have ever heard before! This is Saturday morning and it is usually silent in this neighborhood. Absolutely no wind at all with this sound. What is going on!!!