Summer in Barcelona is the most popular visiting time, but not necessarily the best one. The temperature in summer months often climbs up to 30ВєC or higher, the weather is sunny and humid, and streets of Barcelona are crowded with tourists and foreign-speaking individuals. June is much better in this respect, because it is not that hot yet warm enough for swimming and sunbathing, and the crowds are just starting to gain in numbers. July and August, on the other hand, embody every worst thing about visiting Barcelona in summer. Further, many locals leave the city in August for their respective holidays and leave some restaurants, cafГ©s and stores closed.
Fall, especially September and October, are more welcoming. Milder climate allows for warm days, cool nights and dry weather overall, with rare rains in October. By November the air temperature drops significantly, and in winter it rains occasionally. Every couple years or so Barcelona gets a snowy night, but snow is usually gone by lunchtime.
Spring in Barcelona is a majestic time that lasts a while. Dry warm days are a rule rather than an exception in April, because rains become a rare occasion, and the air temperature climbs steadily. It is already a good time to play beach volleyball and ask for a patio table at a restaurant. By May вЂ“ early June it is already warm enough to swim, and summer is back to Barcelona again.
Thus, depending on your disposition towards hot humid weather and crowds, the best time to visit Barcelona is in May, June and September. If you do not care much about longer queues and prefer 30ВєC to 20ВєC, July or August are fine just as well.