On clear nights in late summer and early fall in the shenandoah valley, why does ground fog form in the low areas near the shenandoah river?

On starry evenings in late summer and early fall in the Shenandoah Valley. The ground haze frame in the low ranges close to the Shenandoah River is cool with dropping air meets damp air in the low regions close to the waterway.

Migration people get up and go cause they feel it is best for them