We're interested in purchasing a vacation lake house in the piedmont/foothills of North Carolina. In earlier summers there, when driving from the mountains home to lower (sub-1000ft) elevations, I've noticed that one has a very distinct sense of descending into a noticeably "yucky" layer of elevated heat, humidity, and haze. (It's actually visible from the right vantage, much as it sometimes is when landing in an airplane).
I think it'd be very desirable for this vacation home to be above this layer. But I don't know how to figure out what the typical elevation of the top of the layer is. I'm not even sure how to define the layer.
So I seek advice on how to quantify what I mean by this "yucky" lower layer of the summer atmosphere, as well as how to determine what its elevation is.