The weather in San Francisco is cool to mild throughout the year, with foggy summers and wet winters. The climate is influenced by the cold currents of the Pacific Ocean which surrounds the city, which in conflict with the California mainland summer heat creates foggy conditions that blanket the city during summer and early autumn. This ensures summers in San Francisco are cooler than inland California. Winters are mild during the day, temperatures seldom dropping below 60°F (15°C), but nights are cold and rain is common. Rain in summer is rare. The most popular months to visit San Francisco are June, July, August, September, October.