Hi Timofey, In this case I think "heaviest" or "greatest" would be correct superlative to use in place of "most". The term snowfall is referring to the event of snow falling (or - and this can be a bit confusing - the amount of snow falling during a given time period). In describing the event, as far as I have seen, we use adjectives like those above. Alternatively one might see the height of snow on the ground post-snowfall (e.g. two feet of snowfall). To use "most" in the correct manner here, you might say, "This was the most snow New York has seen in a 24-hour period since 1869", for example.