Climate of Barcelona

The hills around the city (such as Montjuic) and in the outer metropolitan area, further from the sea, occasionally record frost at night.

Frost during the day has been recorded in the city and inner metropolitan area during the strongest cold waves and snowstorms, but is very rare overall.

[5] As the city lies on a leeward location relative to the westerlies, the largest amounts of rainfall in the cold season are produced by easternly (backdoor) cold fronts or "Levanters",[15] which can last several days[16] and be enhanced when an Atlantic cutoff travels through the Straits of Gibraltar and the Alboran Sea.

[17] So although Atlantic cyclones usually produce little or no precipitation at all, the slipstream effect (rebuf in Catalan) behind a cold front or a trough, when N-NW winds from the Ebro valley ("mestral") and the easternmost Pyrenees ("tramuntana") converge around Barcelona,[18][19] brings rain or, in case of enough low temperatures, snow, as in November 1999.

[20] Especially in summer, when sea surface temperature (SST) is higher, convective precipitation can happen in the form of warm rain[21] (i.e. from the coalescence of water droplets without ice formation) instead of a conventional thunderstorm.

[27] In the 21st century, the heaviest snowfall happened on 8 March 2010, a thundersnow during which public transport and roads were shut down.

The most recent major summer storm was on the 31 July 2002,[36] when over 200 mm (7.87 in) of rain were recorded at some observatories.

Although Barcelona is normally not a windy city,[citation needed] it is affected by sea breezes from May/June to September and winds from the west and northwest in winter.

In winter Barcelona is sometimes affected by the tramontana or mistral winds, like other places in the Northwestern Mediterranean Basin.

[11][37] Snow is rare in Barcelona (falling only once every two years on average), although there are resorts for winter sports in the Pyrenees 100–150 km from the city such as La Molina.

The difference between temperatures during day and night is small because of the strong maritime influence, very rarely surpassing 10 °C.