Well done
You achieved what you wanted to picture. I can see this very well...
I have to say I love the main melody's melancholy seemed whole to me, and that the violas sounded great (if a tad louder then recommended).
The only thing I have to add(mostly this is partial to me) was to make sure that the rain could be heard throughout the whole song, towards the end I couldn't hear any rain... The violas completely took the whole sound. And towards the middle it seemed like the rain jumped a little where the rain sound looped ( 0:37 is where this happens).