Barcelona has a Mediterranean climate, with sub-mediterranean influence, which makes of it not to be the "classical mediterranean climate" with mild, humid winters and warm, dry summers. Barcelona is located in the eastern coast of the Iberian Peninsula, so, the usual west winds, specially in winters, which cause the wet climate in many places of Western Europe, arrive in Barcelona with low humidity, producing no rain. However, the proximity to the Atlantic, its latitude, and the relief, are the reasons why the summers are not as dry as in other Mediterranean Basin countries, because lows (not surface lows but high-atmospheric "cold invasions") can affect easily the area of Barcelona (and Catalonia), causing great storms, particularly in August. Some years, the beginning of June is still cool and rainy, like April and May which, together with August, September, October and November, are the wettest months of the year. The driest are July, February, March and June. So, on average, rainy seasons are spring and autumn, and the dry ones are winter and summer. The order is: AUT-SPR-WIN-SUM. We also have to take into account that the Western Mediterranean Climate is the most irregular of the world. This means that in many occasions averages are not what really happens. For instance, one year October can be very dry and July or February wet months. That's the irregularity. Barcelona and London have the same annual rainfall, but London's climate is not as irregular and torrential as Barcelona's.

As for temperatures, December, January and February are the coldest months, averaging temperatures of 9°C (48 °F) at the Airport and over 10°C in the city. July and August are the hottest months, averaging temperatures of 24°C (72°F). The highest recorded maximum temperature in the centre of the city is 38.6°C.^[16] The coldest recorded minimum temperature was -6,7 °C on the 11th of February 1956 and -5°C the 12th of January 1985. However, in the XIX century -9,6°C were recorded in January 1896. At the Fabra Observatory, situated on the Tibidabo hill, 412 m above the sea level the record summer temperature is C 39.8°C (103.6 °F)^[17] on the 7th July 1982, and the lowest temperature ever registered -10'0º the 11th February 1956. Near the hills and the Airport annual rainfall reaches the 650 mm, and in the city centre about 600 mm.

Snowfalls and freezing nights occur almost one time yearly, though these do not normally lead to significant, if any, disruption. Nonetheless, the city has experienced its share of heavy snowfalls as for example on 1962 Christmas when a true blizzard affected the city falling 50 cm of snow in the city and at least 1 meter at the hills. But, according to ancient pieces of news, in 1887 took place the greatest snowfall, with over 50 cm. The 3rd most important snowfall was in Dec. 1933, with 30 cm in Montjuïc hill. The last ones were on 27th january 2006, 28th february 2005, 29 th February 2004, 18 th February 2003 and 14th december 2001.

Thunderstorms, which occasionally reach severe limits, are common from mid august until november. The latest big summer heavy storm was on the 31st of July 2002 when over 200 mm of rain were recorded in some observatories. Even if Barcelona is not a "windy city" is affected by sea breezes from May/June to September and winds from the west and north-west in winter. Besides, eastern gales (also with rain) cause huge waves in the sea which cause damages to the coast. Sometimes east and NE winds can exceed 100 km/h. In the cold season Barcelona could be affected by tramontana or mistral winds as other places of the Northwestern Mediterranean Basin.

Even if it is considered a sunny city, some days of fog and series of cloudy days are not rare. Sea Fog is usual at the beginning of Spring, when the first warm African air masses overcome the cold mediterranean waters. So, cloudy days could be usual from April to October/November. Winter is more sunny than August. Not July or June.