Multiviscosity oils are identified by their viscosity spread. 10W-30 is essentially 10-weight oil that becomes no thinner than 30-weight oil when heated to operating temperature. 0W-20 is 0-weight that doesn't get any thinner than 20-weight when heated. Lower numbers are better suited to lower cold-start temps. I doubt you would ever need 0-weight oil in Maryland. Up nahth (
), however, it's probably wise to run 5W-something in the winter.
With organic oils, generally the wider the spread, the less stable it is.