I think it means that there are no "wrong" places for a snowflake to fall. In Buddhism, there is the idea that we shouldn't want to change everything. It's better to let everything fall in its place, and not get attached to a certain outcome. When you want the snowflake to fall at a certain place (i.e. when you wish for a certain thing to happen), you become attached to that outcome and it can make you sad when it doesn't fall at that place. Your quote says that no snowflake ever falls at the wrong place (i.e. "Whatever happens, is right"), meaning that you should just accept everything for what it is.
That is my interpretation.