I believe it is trees downed from the tornados.
How long should it season?
To many factors to consider. The tornados where this Spring, and it was cut while the trees where still alive so it is only 3 or 4 months old, I doubt it is ready
Seasoned wood is light, and rings when you hit them together. Wet or uncured wood will give you a dull thud, dry wood will give you a crack or ring. Easiest way is weight, the drier the wood the lighter it is.
The guy I buy firewood from has this on his website: