The main problem is going to be the wind chill, possibly dropping to negative 20 to negative 30 at times on Friday and Saturday. Temperatures are actually dropping below the 0 degree mark Thursday night. Snow starts up on Saturday with Wayne County having the most, possibly seeing more than a foot of snow.
Temperatures are going to be staying absolutely frigid over the coming days, actually dropping below the 0° mark on Thursday night and -- extending all the way out through Sunday morning and will not give above zero. The wind chill will be the major issue as it could drop to around -20 to -30 at times on Friday into Saturday. This means any exposed skin for even a short period of time could start to suffer the effects of frostbite. The mercury will start to climb in to Sunday and Monday getting above the freezing point for the first time since the day after Christmas.
Aside from the cold, snow is also in the forecast. A low pressure system moving up the east coast will also likely cause problems for Rochester, causing lake effect snowfall off of Ontario as a result of the shifting winds.
Wayne County will likely see the most snow, but everyone will get some. Through Saturday evening, snow totals in Monroe and Orleans counties should range between six and 11 inches. In Wayne County, especially closer to the lake, will be more than a foot. Further south of Monroe and Wayne counties, totals will be between one and six inches.