why is san francisco foggy in the summertime
San Francisco fog Under normal summertime conditions, a daily pattern of fog and low clouds occurs. Morning sun heats the ground which in turn heats the marine layer over the land areas. This creates convective turbulence within the marine layer as well as evaporation of any clouds within it. The marine layer clears back toward the coast, usually by noon. By mid-afternoon, inland areas have heated sufficiently to decrease the air pressure and increase the onshore flow. By late afternoon, the wind increases and begins to cool the onshore marine layer, allowing the fog and low clouds offshore to progress inland without evaporating. Cloudiness streams in over the Bay and through the various gaps. How far the clouds can penetrate inland depends on the depth of the marine layer and the strength of the cooling winds. As night falls and inland areas cool down, the winds usually decrease, but the fog and clouds remain wherever they have blown in until the following morning when the cycle repeats.[7]
Climate of Italy In the north precipitation is more evenly distributed during the year, although the summer is usually slightly wetter. Between November and March the Po valley is often covered by fog, especially in the central zone (Pavia, Piacenza, Cremona and Mantua), while the number of days with lows below 0 °C (32 °F) is usually from 60 to 90 a year, with peaks of 100–110 days in the mainly rural zones.[2] Snow is quite common between early December and early March in cities like Turin, Milan and Bologna, but sometime it appears in late November or late March and even April. In the winter of 2005–2006, Milan received around 0.75–0.8 m (2 ft 5.53 in–2 ft 7.50 in) or 75–80 cm (29.5–31.5 in) of fresh snow, Como around 1 m (3 ft 3.37 in) or 100 cm (39.4 in), Brescia 0.5 m (1 ft 7.69 in) or 50 cm (19.7 in), Trento 1.6 m (5 ft 2.99 in) or 160 cm (63.0 in), Vicenza around 0.45 m (1 ft 5.72 in) or 45 cm (17.7 in), Bologna around 0.3 m (11.81 in) or 30 cm (11.8 in), and Piacenza around 0.8 m (2 ft 7.50 in) or 80 cm (31.5 in) [3]