 According to the U.S. Census Bureau, the county has a total area of , of which is land and (4.1%) is water.The county has a hot-summer humid continental climate ("Dfa") and the hardiness zones are 6b and 7a.Almost all of Lancaster County is in the Chesapeake Bay drainage basin, via the Susquehanna River watershed (the exception is a small unnamed tributary of the West Branch of Brandywine Creek that rises in eastern Salisbury Township and is part of the Delaware River watershed).