The earliest dates when snowfall occurred in the cities of New York, Boston and Philadelphia.
The earliest date that New York City has had snowfall was October 10, 1925, and October 10,1979, when trace amounts fell in Central Park. The earliest date that measurable snowfall amounts fell in the city was October 15, 1876, when 1/2" fell in Central Park. The earliest date when 1" or more of snow has fallen in New York was November 5, 1879, when 1.5" of snow fell in the park.
Update: On October 29, 2011, a total of 2.9 inches of snow fell in Central Park. That was the first time NYC history that over 1" of snow fell in the city in the months of October.
Where I live in Northwest New Jersey, we received 16" of snow on October 29, 2011. That broke all records for snowfall in October, and caused my home to lose power for five days.
Only three times in New York City weather history, dating back to 1869, has measurable snowfall occurred in the city in October. Fifteen times in New York City history has trace amounts of snow fallen in the month of October.
Image Source by Cliffy
Where I live, in northwestern New Jersey about 45 miles from New York, we had a major snowfall weather event on October 28, 2008, just three years ago. On that date, some six inches of snow fell in my area, and over 1 foot fell on top of a mountain near me. I had to go pick up the kids from school, and one of them asked me to drive her friend home, who lived on the mountain.
After almost getting stuck a couple of times, and helping out a few other stuck drivers, I managed to drop the friend off and drive off that mountain through the two worn tire tracks in the snow. It was a nightmare, nobody is ready for that much snow before Halloween. Especially not Mother Nature.
With leaves still on many of the trees, the heavy snow that fell that day caused countless tree branches to snap like matchsticks. You could hear them breaking with a popping sound all over the place. One of the branches knocked out a major power line on the mountain, and people up there were without power for days.
Image Source by Ralph Hockens (Snow in Central Park in New York City)
In regards to earliest snowfall dates, New York has been lucky compared to Philadelphia. The City of Brotherly Love actually had 2.1" of snow fall in the city on October 10, 1979. Philadelphia also got 1.5" of snow on October 20, 1940, and 1/2" of snow on October 19, 1940.
The snow that fell on October 10, 1979 in Philadelphia, and only left trace amounts in New York City, also made it to Boston. Boston got its earliest measurable snowfall on that date. Just two-tenths of inch fell in Boston on October 10, 1979 though.