According to the U.S. Census Bureau, the county has a total area of 788 square miles (2,042 km?), of which, 754 square miles (1,952 km?) of it is land and 35 square miles (89 km?) of it (4.38%) is water.
Napa is warmer in the summer than Sonoma County to the west or Santa Barbara County, a wine-producing county in southern California. Thus, the Napa wineries favor varietals such as Cabernet Sauvignon, while Pinot Noir and Chardonnay are more the specialty of Sonoma wineries and Santa Barbara wineries. At the north end of Napa County, in the Mayacamas Mountains, lies Mount Saint Helena, the Bay Area's second tallest peak at 4,344 feet (1,323 m) and home to Robert Louis Stevenson State Park. At the west side of the Napa Valley is Hood Mountain, elevation 2,750 feet (838 m).
Napa County is home to a variety of flora and fauna including numerous rare and endangered species such as Tiburon Indian paintbrush and Contra Costa goldfields.
