The kids are heading back to school, the weather is still warm and the sun is still shining – making New York City in September an ideal destination. Check out a ball game at Yankee Stadium, have dinner in Little Italy during the San Gennaro Festival, or grab a water bottle and explore the city with one of the many walking tours available. New York Yankees & Mets Baseball GamesSports fans visiting the city in September should take themselves out to a Yankee or Mets game, particularly because both teams have moved into brand new state-of-the-art stadiums. Baseball aficionados wanting to delve into the rich history of the game will…