We spent the New Year Holiday visiting friends in Saranac Lake, NY in the Adirondack Mountains. The temperature on New Year's Eve was in the single digits, at the Adirondack Park Visitors Interpretive Center (VIC) in Paul Smiths, NY. When we snowshoed up Dewey Mountain near Saranac Lake on the first day of 2009, the temperature was minus four degrees Fahrenheit.
The D70 worked fine, but do not leave your camera on when you are not shooting - it will help save your battery. I strongly recommend placing the entire camera in an airtight plastic bag before you take it into a heated house. To prevent major condensation - Do not take it out of the bag until it has come up to room temperature.