An all-night party for saints and swimmers

The cities empty and the beaches fill on La Noche de San Juan.

It's late and the light is fading. A schooner is moored in the bay, its elegant sails mirrored in the sheer blue water. The shore is flecked with hundreds of bonfires, their thin flames snaking into the night sky. The noise from the beach is deafening as we walk through groves of sugar cane to check out the action. The scene that greets us is pagan, tribal, hedonistic.

It's late and the light is fading. A schooner is moored in the bay, its elegant sails mirrored in the sheer blue water. The shore is flecked with hundreds of bonfires, their thin flames snaking into the night sky. The noise from the beach is deafening as we walk through groves of sugar cane to check out the action. The scene that greets us is pagan, tribal, hedonistic.

Picture a Spanish fiesta crossed with a Goan rave and you get a flavour of La Noche de San Juan, the midsummer festival celebrated all along the Malaga coast. The event combines the saint's day with the start of summer. Saints days are more important to Spaniards than birthdays and as Juan is the most popular Spanish name, the day has a special power. Add to that the 40C temperatures in cities such as Seville and Granada and there is an incentive for everyone, whatever their name, to pack the camping gear and head for the coast.

We join the party in Nerja, a small seaside town about an hour from Malaga. Nerja has a number of festivals throughout the year and is a town that knows how to party. Like all the places along this stretch of Andalusia, visitors have been arriving all day. By the time we go for lunch on the main Burriano Beach, it already looks like tent city.

We prepare for the long night ahead by eating at Ayo's restaurant. Ayo is credited with discovering the Caves of Nerja, now a top visitor attraction, when he was a boy out on a bat-hunting expedition in 1959. Now an enormous man with a long greying ponytail, he looks like a Dante-esque hockey player in his shorts and protective leggings, cooking pans of steaming yellow paella over fierce open fires.

But his restaurant is heaven. The smiling waiters balance multiple plates as they run down the lines of tables, shaded by a grapevine canopy. The place is packed with diners, drinking jugfulls of iced gazpacho with their paella or rich lamb stew – a kind of giant Mediterranean school dinner. The beach is packed and the atmosphere in the town is electric.

It is forbidden to have barbecues on the beaches at other times of the year: San Juan is the only opportunity and people make the most of it. We meet friends mid-evening and pitch camp in one of the smaller coves. It's calmer than Burriano with just a few large families camped out. Like them we make a fire from driftwood and build a barbecue with stones and bricks scavenged from among the rocks and cacti framing the cove. After eating grilled chorizo so spicy it makes our lips tingle and drinking chilled red wine, we wander along the coastal walkway towards the rising noise level. The scene is astonishing in its intensity. The main beach is now six-deep in tents. At the edges are those who staked their claim earlier, some in settings so grand they resemble a genteel garden party. Extended families sit under white canopies at long tables stacked with food. Tablecloths flap in the breeze, generators hum, barbecues sizzle.

We pick our way into the belly of the beast. Here younger people have vied for every last inch of available space to pitch smaller tents and dig deep holes for their bonfires. You can barely move for tent pegs, children, dogs, noise. Deep in the middle there's a municipal main stage, an official bonfire and a pay bar, but most people have set up for themselves, surrounded by carrier bags full of food and drink. Portable sound systems pound out competing varieties of rave music.

We head back to our own beach and can almost feel the excitement rippling along the coastline as people wait for midnight. There are shadows of bodies on the rocks as people climb to get a better view of the scene playing out on Burriano. Some let off firecrackers as a prelude to the main event and their sound echoes around the rocks.

Suddenly, it's midnight and fireworks shoot into the sky. Hundreds of people teem into the sea like lemmings, their bodies silhouetted against the bank of orange flame lighting the shoreline. We race in to join them, gasping at the shock of icy water after the warmth of the fire and the alcohol.

Soon the dark surface of the water is broken by white bodies bobbing like buoys as people of all ages splash around. The fireworks burst above our heads like giant alliums, their sparks drifting down to meet the flying embers from the fires. We swim out far enough to see the climax of the display – a huge roman candle flaring in the centre of the beach, its silver plumes cascading into the sea.

San Juan marks the first day that locals feel it is comfortable enough to swim, but few can bear the traditional midnight dip for long. People come shivering out of the sea and stand swaying in the firelight, hugging their towels, while the bravest take turns to jump the flames, a ritual said to bring good luck for the coming year. The fire-jumping is followed by a slice of Torta de San Juan, a traditional cake whose chewy consistency can only be described as being like that of the inside of an old teddy bear. As the night breeze drifts in, groups huddle closer to the bonfires, chatting, drinking and dancing.

By 2am, the wood smoke hangs thick in the air and floats out over the still water in a low pall. The celebration is still visible for miles around, with fires twinkling along the coast. Some people doze and children hang heavy in their mothers' arms. A few disappear into to their tents for the night. But there are still huge crowds heading for the main stage or up to the many beachfront bars cranking out dance music.

The smoke haze and the throb of sound systems continues into the morning. Many have been drinking and partying for 12 hours or more but the atmosphere is relaxed. There isn't a policeman in sight. We leave at around 4am and wander home through empty streets. The music continues to blast till dawn finally finishing at around 8am, appropriately enough with that club classic "Insomnia" by Faithless. Half an hour later and the church bells start ringing. You can count on the Spanish to stretch the shortest night into a day to remember.