I think OP wanted to construct “sand by induction”, but I also think you need more than one grain. If you have 9 grains of sand and add one snowflake, you now have something that’s 90% sand and is therefore 10 grains of sand. Take your 10 grains of sand and add another snowflake to create 11 grains of sand. Continue with each snowflake one by one, and you’ve inductively created a sand pile.
You don't need to construct sand by induction. Just notice that snow has the right particle size to be considered sand.