Definitely July! We have lots of parks and green spaces that are bare in April but lush and beautiful in July. It's just a prettier place then. The days are longer too. And everyone seems to live outside, with lots of sidewalk cafes, rooftop and garden restaurants all over the place. There are also lots of outdoor activities, from free kayaking to free outdoor movies, plays and concerts, and picnics of course. And all kinds of river cruises, from fine dining to twilight wine cruises. Don't forget that there are some wonderful beaches nearby. If you don't have time for a trip to the Hamptons, take a day trip to Fire Island, Long Beach or Far Rockaway, or nearby Brighton Beach.