Before we succumbed to sleep, we heard a “who ?”. Now, around this time of year, we tend to be visited by Screech Owls, but they sound more like crazy jungle birds than hoot-owls. We heard them (much earlier in the evening) a few weeks ago.
But this was an honest-to-goodness wh-hoo, and there's only one kind of owl that visits these parts that sounds like that: a Great Horned Owl. It would be so cool to see one of them: