I felt the same, whenever I went sailing in the Long Ship back when Valheim was first released the sun was out and blue skies day time and I loved exploring.
The only time I saw storms was at night and that brought out the sea serpent as he is tied to night storms.
Now as soon as I get away from my base clear skies and sunshine the skies darken and its full sleat rain lightning like its calling the sea serpent out in the day time.
I dont mind rain but I want see the beautiful Valheim biome coastlines as I sail around and explore it happens everytime.
As for the sea serpent he shouldnt be appearing in the day time storms..