August is the warmest month with spikes surpassing 90 degrees Fahrenheit. Milder weather prevails in October, when temperatures average 70 F during the day and 54 F at night, according to the government's Agencia Estatal de Meteorologia. October also claims the highest average relative humidity of any month at 75 percent -- only slightly higher than the annual average of 72 percent. July is the driest month in Barcelona, averaging 69 percent humidity.
October has the highest average rainfall at 3.6 inches per month -- only slightly higher than September's tally but significantly higher than the annual per-month average of 2.1 inches. October's average of six rainy days per month -- another Barcelona high -- is only slightly more than the annual average of 4.5 days a month. In fact, every month tends to have four to five days of rainfall except for July, which typically has two. Lonely Planet notes that September and October are prone to thunderstorms.
If visiting Barcelona in autumn, pack for both cooler and warmer temperatures. Lighter clothing will work most days, but a sweater or jacket may be necessary at night. Warmer clothing is especially important later in the month. Temperatures drop more rapidly the closer the calendar comes to November, which averages nighttime temps around 46 F. Due to the heavier rainfall and possible thunderstorms, bring a rain jacket or umbrella.
Frommer's notes that the sea water is still warm enough for swimming in early October, but later in the month, consider heading south to the Costa del Sol and Costa de la Luz beaches in the Andalusia region. Due to more moderate temperatures, October is an ideal month for comfortably walking La Rambla and other major city streets. October is also considered off-season, which means fewer tourists and lower hotel prices. As far as major events, the Barcelona Jazz Festival and Barcelona International Gay and Lesbian Film Festival both typically launch in October. Likewise, the Fiesta Nacional de España occurs each year on Oct. 12 in celebration of Christopher Columbus' discovery of America, a voyage that was partly financed by Spain.
