California is the undisputed leader in wine production in the United States, accounting for 85% of national production. As the world's 4th largest wine producer, California is recognized for its exceptional quality wines, particularly thanks to its ideal climate influenced by the Pacific Ocean. California's coastal wine regions enjoy an oceanic climate while the inland areas near the Sierra Nevada have a more continental climate. Napa and Sonoma Valley are particularly renowned for their premium California wine, thanks to the bays and openings to the sea that act as thermal regulators.