Grey Sky darkening -Evening Run

To run 
Is instinctive,
The fresh air 
Coursing through; 
Finding energy 
Where first there is none;
To tread the lanes 
As day is done;
Though tired, to feel renewed,
Spurred on by the towering clouds behind, 
The wind coursing in the pines 
Grey sky  darkening 
Squeezing out the light; 
The onset of a stormy night.
Yet invigorated, 
energised,
With wind in the face
I can pick up speed 
Increasing the pace.