The only element of the ritual that makes a smidgen of meteorological sense is recognizing springtime is a season of stormy change from a season of just plain cold/dry. With the latter being mostly sunny, and the former being mostly cloudy, that suggests seeing a shadow means your still stuck in non-stormy winter, while not seeing it means you are more in season-change mode, or more in Spring conditions.
Good point. But the hedgehog is a nocturnal animal, so it won’t apply to him. However, it is also a hibernating animal, and such are rather good at predicting when Spring will arrive: after all, their lives may depend on their being right.