San Diego has one of the most consistently pleasant climates of any US city. The best weather is September through November and March through May, when temperatures range from 18C to 24C and coastal fog is minimal. Late September and October, sometimes called 'Second Summer', bring warm and clear conditions to the beaches at La Jolla, Pacific Beach, and Coronado. The San Diego Comic-Con International in July is the world's largest pop culture convention and books up hotel rooms for 50 miles around; book well ahead if attending. June is marked by the 'June Gloom' marine layer that covers the coast in morning fog until noon. July and August are warm, 22C to 28C, and the most popular beach season. December and January are mild (13C to 18C) and the quietest months for tourism. The San Diego Zoo is best visited on weekday mornings. Balboa Park's museums are open year-round and provide excellent rainy-day options, though rainy days are rare.