In the winter New York is a few degrees warmer than surrounding areas due to its coastal location and high urbanization. However it is still rather cold in the city. As warm fronts coming from Mexico collide with cold fronts from Canada the wether is unstable and can change from warm to freezing in several hours.
The average winter temperature is usually above freezing. But occasionally it can drop as low as -15 °C. Chilling wind makes it feel even colder. Snowfalls are frequent starting from December but snow rarely stays on the ground for long. Snowstorms happen during the winter, which may cause roads and airports closure.
If the wind blows from the South, weather can be quite mild, sunny and pleasant. There are also plenty of cool clear and sunny days which are good for sightseeing.