Manhattan - Upper East Side in December

April through June is magical here - Central Park explodes with cherry blossoms and the museum crowds haven't hit summer peak yet. September through November might be even better: crisp air, perfect for museum-hopping, and the fall foliage in the park creates Instagram gold. Winter has its charm if you can handle the cold - the Met's Egyptian wing feels extra cozy when it's snowing outside, and holiday window displays along Madison Avenue are legitimately spectacular. Summer gets sticky and crowded, especially around the museums, but the outdoor concerts in Central Park make it worthwhile. Just book hotels way in advance if you're coming during Fashion Week in February or September.