I dont think I would say snow is clean,,,
I would not use any water from my wells without testing at least 2 times a year. (would be the same for the spring water I know that has iron bacteria in it) One never knows where the powers that be put an injection well, we have had 2 near me shut down!
I have questions as to whether or not tap water is safe,,,but thats another issue.
Rain water goes down hill to the lakes, then is collected, filtered, tested, treated and called safe.
For my personal use I have a RO system and do not drink tap water!