Photo looks overexposed, making the cement sidewalks and road appear like they have a thin later of snow. But, to the right of the woman with stroller, the "grassy knoll" does look like it has a thin layer of snow/ice remaining on it?.  Maybe the picture was taken in February or March? Did NYC get any snow in March-April? Possibly dew on the grass with lighting and overexposure making it look like snow? I dunno.