Britain is finally discovering the summer joys of open-air cinema

The first time I saw a film in the open air was in Paris in 1997. Showing on the big screen in the gorgeous surrounds of the Parc de la Villette was Ken Loach's Riff-Raff. At the time, sitting waiting for the sky to darken with a group of friends, a blanket and a picnic seemed positively alien. Movies were meant to be watched in cinemas or on video with the curtains drawn.

But I'd wanted to see a film under the night sky ever since I had my first taste of outdoor cinema, which bizarrely came at home on video. Watching Francis Ford Coppola's The Outsiders, I was enamoured when the Greasers, played by Ralph Macchio, C Thomas Howell and Matt Dillon, went to that bastion of early Fifties Americana - the drive-in movie. What was most fascinating was that the Greasers didn't even have a car; they watched the movie from plastic seats at the back of the park. The lack of an automobile demonstrated that it wasn't the cars that were "cool" about the experience, but the romance of watching the silver screen under the stars.

The past decade has seen alfresco movies take off in the UK. As video ate into cinema revenues in the late Eighties, distributors searched for new ways to excite audiences into watching films away from their sofas. The multiplex catered for new releases unavailable on a home format, but something more was needed to get audiences interested in seeing classic and cult favourites on the big screen again. The solution has been open-air cinema.

Summer open-air screenings have emerged as an annual fixture up and down the country. The Serpentine Gallery and Somerset House have led the way in London, the Spa Suncourt on Scarborough's coastline will be showing a selection of films for the second year in a row, and Screen Machine, a mobile cinema with 102 seats, travels around the Highlands and Islands of Scotland throughout the summer. Even the Edinburgh Film Festival has started putting on movies under the stars.

Sally Tallant, head of education and public programmes at the Serpentine Gallery, says: "I don't really know why watching screenings in open air has become such a recent phenomenon. Part of it is definitely the collective element. Sitting in a park, with a picnic, with 5,000 other people all sharing in the moment is just terribly romantic."

Judging by the success of Stella Artois Live, an event billed as "the UK's first outdoor film festival", this is not just a passing fad. The festival took place in Greenwich Park over a weekend in July and proved that it's not just romance that makes outdoor screenings so popular. On the Saturday, 7,500 people enjoyed a Japanese themed-day that preceded a showing of Quentin Tarantino's kung fu epic Kill Bill. On the Sunday Greenwich Park erupted as the National Symphony Orchestra played the Ghostbusters theme tune. Ten thousand revellers boogied to the sounds of the Eighties before a screening of John Hughes's Ferris Bueller's Day Off. The lack of a roof completely liberated the audience. As Ferris Bueller sang "Twist and Shout", everyone in the audience started singing and dancing.

The enthusiastic reaction to Ferris Bueller also shows how some films work better in an open-air environment than others. Tallant argues that you have to consider the setting when programming a film. "At the Serpentine, we try to gauge how the film will look in the space that we are showing it in. One thing that excites me about showing Blue Velvet this year is the opening sequence, in which the camera pans through a window and leads us to a dismembered ear into the grass. It's bound to have an incredible impact on an audience that is watching the sequence sitting on a patch of grass."

There remains the question of what happens when it rains. But the idea that an alfresco event would be ruined by wet weather was consigned to the dustbin by a 2004 screening of Battleship Potemkin in Trafalgar Square. Despite the pouring rain, thousands of people watched as the Pet Shop Boys provided a live musical accompaniment to Sergei Eisenstein's 1925 classic. And last year a screening at the Serpentine Gallery of Alfred Hitchcock's Vertigo saw crowds come out in force despite the rain. Tallant says: "People were using plastic bags as makeshift tents and there was this camaraderie amongst the audience that was fantastic. It turned out to be very exciting."

Serpentine Gallery, Kensington Gardens, London W2 (020-7402 6075) shows 'Performance' tonight and 'Blue Velvet' tomorrow; Film4 Summer Screen, Somerset House, Strand, London WC2 (020-7845 4600), 10-19 August; The Mound, Edinburgh ( www.edfilmfest.org.uk/underthestars), 11-12 August; Spa Suncourt ( www.film scarborough.com) shows 'Touching the Void' on 10 August