Fernley is located at the intersection of Interstate 80, U.S. Route 50 Alternate, and US 95A. Although it originally spanned the Lyon/Washoe County line, a county boundary change in 2005 left it entirely in Lyon County.
According to the United States Census Bureau, the CDP had a total area of 35.4 sq mi (92 km2), all land.
Fernley's climate is typical of high desert environments. The winter may bring cold temperatures and some snow, but nothing extreme is normally experienced. Summers are generally hot and very dry. Fernley's average annual rainfall is 5 inches (130 mm) per year.