Spain is blazing with poppies, orchids and wild flowers at the moment, but with Semana Santa, Holy Week, and Easter upon us, a riot of human colour is also erupting across the country. During Holy Week, processions sway and thump through towns and villages decked out in the full regalia of church and Inquisition. Semana Santa (April 8-15 this year) heralds the approach of Spain's fiestas and ferias (local fairs), and the start of the bull-fighting season. There is hardly any time of year when a village or hamlet is without some feast or other, but May to July sees some of the most beautiful and dramatic, especially in the south. Prices go up dramatically during Feria and it is always advisable to book a hotel well in advance. Then again, you may not go to bed at all.

Seville (April 29-May 7)

The best way to irritate a rural Andalucian is to tell them that nobody parties like they do in Seville. The Holy Week pageants are some of Spain's most moving and Sevillians will certainly claim their April Feria is the best. From the moment the lights go on in the Real de La Feria, the city hardly sleeps for a week. Not that Sevillians are very good at getting to bed at any time of the year, but the Feria is their chance to prove their stamina.

Whole families emerge from their houses dressed like a picaresque tableau, with even the tiniest children done up like pocket Carmens. But then Seville is the home of the cigarette factory that inspired Bizet's best tunes. Round a corner you will hear clapping and be confronted by the spectacle of a spontaneous Sevilliana, the local dance that is quick to pick up and essential if you want to enjoy the party. In the afternoons, the Sevillian horses clip-clop under the orange and lemon trees, often more brightly attired than their riders. The city plays host to several funfairs, too, and the best flamenco bars are to be found along the Calle Vetis.

• For further information, visit: www.sevilla.org. Tourist Office: Avda de la Constitucion, 21b. Tel: 00 34 954221404.

Granada Cruces De Mayo (May 2 and 3); Summer Fair of Corpus Christi, (June 14-21); International Music and Dance Festival (June 22-July 8)

Granada, home of the Alhambra, bursts into colour during Cruces De Mayo, on May 2 and 3, when windows, balconies and patios are adorned with floral crosses. This is followed by the Feria of Corpus Christi, which is given much of its flavour by the fact that Granada is a university town, and young as well as old dress up in traditional garb. The city has the added attraction of the gypsy caves at Sacramonte, where you can see flamenco most days of the year. But be warned, the place has become very touristy and exploitative and it is always best to make friends of a local who can show you the more authentic spots. This year is the 50th anniversary of Granada's annual International Festival of Music and Dance (June 22-July 8).

• For information and booking, visit www.granadafestival.org, Tourist Office: Corral del Carbon. Tel: 00 34 958225990

Jerez Feria De Caballo (May 13-20)

For my pesetas, Jerez has the finest feria of all. It centres around the park Gonzalez Hontoria and for a week under the jacaranda trees, this elegant, wealthy town - home of sherry, bull breeding, flamenco and the Spanish Riding School - becomes a vignette of old España. It is a true horse fair and they do things in style. Here you will see some of the finest examples of Andalucia's famous dancing horses alongside almost every equine breed under the sun, while there are riding competitions and the grand parade of riders and carriages.

Couples in traditional Traje (polka dot dresses for the women and gaucho hats, chaps and waistcoats for the men) really indulge in the Spanish talent for flirting and display. The paseo, the evening stroll, is raised to a fine art in Jerez. Casetas - bars-cum-restaurants -pump, the death rides at the fun fair spin the pretty doñas like bunches of wild carnations and the caballeros strut their equestrian stuff.

• For further information, visit: www.jerez.org. Tourist Office: Calle Larga 39. Tel: 00 34 956331150

Cordoba Cruces de Mayo (May 1-3); Festival de los Patios Cordobeses (May 4-16); Nuestra Senora de Salud (May 20-28)

As in Seville, beautiful Cordoba makes much of Semana Santa. But its feria, of Nuestra Señora de Salud, is gentler than Seville's and is at its most entrancing when the Juderia, the old, labyrinthine Jewish quarter along the side of the Mesquita (mosque) begins to jostle with costumes and dancers. For a very unusual festival, visit the Festival de Patios Cordobeses a week before. The city will probably be less full and accommodation easier to find for the ensuing party. The Spanish patio has its roots both in Roman and Arabic culture and families unlock a floral and architectural treasury, hidden for the rest of the year behind sturdy iron grates, as they compete to delight visitors and win prizes. Cordoba also hosts a flamenco festival every two years, this year April 27-May 12, and a festival of guitar in the first two weeks of July.

• For further information, visit: www.ayuncordoba.es. Tourist Office, 10 Palacio de Congreso. Tel: 00 34 957471235

Madrid Fiesta De San Isidro (May 15 for two weeks)

It's entirely appropriate that stolid, grandiose Madrid should begin its biggest fiesta, dedicated to the city's patron saint, San Isidore, with a speech. The Pregon is delivered by the mayor on the day of the saint, even if no one's listening, and then the games begin. The capital may have little of the intimacy of, say, Jerez or Cordoba, but it has its own attractions and the Fiesta of San Isidro is especially significant as it heralds the start of the capital's bullfighting season, and for bull and matador alike all roads lead to Madrid. There is also a public party on May 2, the Festival of St Antonio in August and any number of local events.

• For further information, visit: www.comadrid.es and www.munimadrid.es. Tourist Office: Calle de Duque de Medinaceli 2. Tel: 00 34 914294951

Huelva Virgen del Rocío (June 1-4)

If a foreigner tells a Spaniard he is a 'Rociero', he'll probably be met by a slightly resentful grimace at such impertinence. The pilgrimage - or romería - is not for tourists and to follow the Camino (the way) through the Cota Donana National Park, you really need to be invited along by one of the Brotherhoods, semi-religious guilds that set out in full costume from villages right across Spain. They converge on the little town of El Rocio, following their local virgins in flower-decked carriages pulled by oxen. There, after days of ecstatic partying, the young men of the mountain town of Almonte, and only they, literally fight for the right to manhandle a huge silver Madonna around town. "The Paloma Blanca", or White Dove, as she is called, is said to be the source of many a miraculous cure, and to take "the promise" to join the pilgrimage is probably the Andalucian equivalent of going to Mecca, rivalled only by the more sober northern route of Santiago del La Compostela. Part religious festival, part pagan rite, all the traditions, prejudices and superstitions of Andalucia converge at the little town.

It is possible at least to watch the start, and one of the best places is Sanlucar de Barrameda, from where Columbus set sail in 1492. The procession that leads the virgin is splendid and there is little to compare with the sight of army landing craft carrying the horses and pilgrims across the Guadalquivir river and into the national park. Sanlucar also hosts a sherry festival in early April, flamenco, jazz and music festivals and its famous beachfront horse races in August.

• Further information from the Sanlucar Tourist Office, Calzada del Ejercito. Tel: 00 34 956366110.

Pamplona The Running of The Bulls (July 6-14)

Spain's most famous fiesta. Immortalised by Hemingway in The Sun Also Rises, a novel slimmer than a cape, the festival of San Fermin is when the young men run with the bulls, someone invariably gets badly hurt or even killed, and the tabloids start running their campaigns about Spanish cruelty to animals. The fiesta itself is a feast of fireworks, music and processions, rich in tradition and spoilt perhaps only by the sheer weight of visitors. The dangerous bit, for humans at least, is when the bulls are let loose every morning from the Coralillos of Santo Domingo to run the course to the town's ring, where the daily fights take place. To take part, you will have to be at the start before 8am when rockets signal the beginning of the mayhem. Pamplona can be one of Spain's most exciting and most upsetting fiesta, but one of its nicest moments is when it winds up on July 14 with a candle-lit procession.

• Tourist Office: Calle de Duque de Ahumada 3. Tel: 00 34 948220741

Malaga Feria (August 11-19).

As if in penance for the extremities of their coastline, the Malagans celebrate Semana Santa with more solemnity and gravitas than anyone else. The thrones carrying the holy images through the faded grandeur of Malaga's streets need up to 200 people to bear them along. But Malagans have always known how to have a good time and their feria is one of the most exuberant.

In the day, the fun takes place in the streets and bars across the city and at night switches to the Cortijo de Torres on the edge of town. It is also a place to see two unique dances, Verdiales and Malequenas.

• Further information from www.malagaturismo.com. Tourist Office: Pasaje de Chinitas, 4. Tel: 0034 952213445

• For further details of ferias and fiestas across Spain, contact the Spanish Tourist Board on 020-7486 8077.

For Andalucia, check out www.andalucia.org

David Clement-Davies' novel Fire Bringer is published in paperback by Macmillan. His second novel The Sight will be published later this year.