The atmosphere of the game is great! And I really like the hand drawn art style and the melancholic music at the end where you see the "storm". (Yes, I have beat the game and the difficulty was brutal :-D) Btw. I am still listening to the end music while writing my post here.
If I can suggest something, I'd say, maybe have a music track with a longer melody in the loop for the main part? It became slightly repetitive, especially because I tried the boss multiple times and had to walk all the way back to it.
All in all I really like how you interpreted the "calm before the storm" theme.