Barcelona has a Mediterranean climate (Köppen climate classification: Csa), with mild, humid winters and warm, dry summers.
Its average annual temperature is 20 °C (68 °F) during the day and 11 °C (52 °F) at night. The average annual temperature of the sea is about 18 °C (64 °F). In the coldest month – January, the temperature typically ranges from 8 to 17 °C (46 to 63 °F) during the day, 2 to 10 °C (36 to 50 °F) at night and the average sea temperature is 13 °C (55 °F). In the warmest month – August, the typical temperature ranges from 25 to 31 °C (77 to 88 °F) during the day, about 20 °C (68 °F) at night and the average sea temperature is 25 °C(77 °F). Generally – the summer / "holiday" season lasts about six months, from May to October. Two months – April and November – are transitional; sometimes the temperature exceeds 20 °C (68 °F), with an average temperature of 17–18 °C (63–64 °F) during the day and 8–9 °C (46–48 °F) at night. December, January and February are the coldest months, with average temperatures around 14 °C (57 °F) during the day and 5 °C (41 °F) at night. Large fluctuations in temperature are rare, particularly in the summer months.
Barcelona has average several rainy days per month (≥ 1 mm) and annual average relative humidity is 72%, ranging from 69% in July to 75% in October. Sunshine duration is 2,524 hours per year, from 138 (average 4.5 hours of sunshine a day) in December to 310 (average 10 hours of sunshine a day) in July
