I can’t think of any other ‘it’ that is meaningless. ‘It’ normally refers to something in the sentences context. But in that and in the sentence ‘it rains’ there is nothing that ‘it’ could refer to. The sky doesn’t snow, the weather doesn’t snow and neither do the clouds.
No one on planet earth says “It rains” or “It snows”. The phrase is “It’s raining out”. It meaning the environment, or more specifically, the sky. I’m not sure why you dismissed the sky, initially, but that’s where precipitation generally comes from, and it covers all of “out”.
You don’t live where it snows or rains?