Here are some popular events in Spain by month:

January - Three Kings Parade (Dia de Reyes Magos) in various cities, Hair of the Dog Festival in Malaga

February - Carnival in Cadiz and Tenerife, Almond Blossom Festival in Mallorca

March - Las Fallas Festival in Valencia, Sitges Carnival near Barcelona, Moors and Christians Festival in Alcoy

April - Feria de Abril in Seville, Semana Santa (Holy Week) celebrations in various cities

May - Feria de Cordoba, Feria de Jerez (Jerez Horse Fair)

June - San Juan Festival (Midsummer) in various coastal towns, Sonar Music Festival in Barcelona

July - Running of the Bulls (San Fermin) in Pamplona, Benicassim Music Festival

August - La Tomatina Festival in Bunol, Semana Grande in San Sebastian

September - La Mercè Festival in Barcelona, Flamenco Festival in Seville

October - Fiesta del Pilar in Zaragoza, Autumn Fair in Malaga

November - All Saints' Day (Dia de Todos los Santos) celebrations throughout Spain, San Diego's Day in Madrid

December - Christmas markets and celebrations in major cities, New Year's Eve celebrations in Puerta del Sol, Madrid