New York City to Niagara Falls must be about an 11 hour drive (just a rough guess; someone else might have a closer figure) each way so it is definitely NOT a day's drive. You would probably have to fly into Toronto and rent a car. However, Niagara Falls is definitely worth seeing, in my opinion. Take the Maid of the Mist boat ride to get close to the falls (they hand out rain coats so that you don't get soaked from the mist from the falls!)

Helen Ottawa, Canada