As British summers get warmer - perhaps because of global warming - jerseys are being left forgotten in wardrobes, naturism is booming, sales of sun creams are soaring, and gardens everywhere are being furnished as once only rooms were, with sofas, tables and chairs. So, for that matter, are pavements. Open-air Britain is arriving.
It is more than just impression. The double trend, of warmer weather and a corresponding change in lifestyle, can be illustrated statistically.
British summers have got markedly warmer this century, and recently they have also been getting longer. Figures collected by the fastidious Climate Research Unit at the University of East Anglia show that average summer temperatures have risen by nearly 1.2F since 1901, a significant increase. Autumns have warmed even more, by nearly 1.7 degrees.
Over the past two decades springs have got warmer, lengthening the summer. Britain's two hottest-ever long summers - measured from May to October - were in 1989 and 1990: 1976 was hotter but only over the shorter period of June to August. The present heatwave is thought to be the hottest spell since August 1990.
This warming trend is being paralleled by a new pattern of al fresco social life. The warmth is clearly not the only cause: increased preoccupation with leisure over the last 30 years, and increased affluence, have clearly been major factors in the move to life in the open air. But warmer weather certainly provides the context and has facilitated the change.
The change itself is visible in some delightfully obscure statistics. Take knitwear sales. Sweaters, pullovers, cardigans and jumpers sold in the UK fell from a total value of pounds 158m in 1981 to pounds 135m in 1992. The trend has been steadily down, falling successively even in the peak years of the Thatcher consumer boom of 1987, 1988 and 1989.
John Harrison, of the Knitting Industries' Federation, personally doesn't agree with the weather theory. "I don't think it's as a result of the apparent warming climate in this country. More significant changes have been brought about by fashion."
But he does not deny the change in lifestyle is there. "Overall, we're wearing lighter garments." And one garment especially, redolent of nippy mornings, seems to have vanished. "Many people, particularly males, have dispensed with vests almost universally."
The number of people who wear fewer garments is clearly also on the increase, to judge by the sales of suncare products, which have grown by 82 per cent since the beginning of the decade alone, according to the market research agency Mintel. Around pounds 113m will be spent on suncreams this year, compared with pounds 59m in 1990. Ten per cent more men are using suncreams than 10 years ago [54.7 per cent] although only 2 per cent more women [59.4 per cent] are.
Some people, of course, choose to wear no garments. Their numbers are steadily increasing, too. There were 16,471 members of the Central Council of British Naturism in 1988, and19,679 last year. Gerry Ryland, who was president for 20 years, estimates members have trebled since 1980 and thanks the weather. "When it's hot they get them off," he said.
Our changing eating habits are also evidence of the move to open-air Britain. Two years ago London's Westminster Council licensed 20 restaurants for pavement cafes. Today there are 54.
"The growth of cafe society can mainly be put down to climatic changes," said a council spokesman. "The summers are warmer and as soon as you get a nice spell like this, the tables and chairs come out. We expect the explosion in pavement cafes to continue."
"I think the British lifestyle has changed," said Ann Barr, associate editor of Harpers & Queen and co-author of The Sloane Ranger Handbook. "If you go down the street now - Kensington Park Road for example - it looks just like Paris with the tables on the pavement."
Other cities, such as Leeds, are witnessing the pavement cafe phenomenon, which may have an added explanation.
Some experts think cities have been heating up even faster than the country as a whole, becoming "heat islands" as they get larger and swallow up green space, and as traffic increases, burning more energy.
But the real explosion in British al fresco dining is away from the pavements and behind the privet hedge. It's dejeuner sur l'herbe: you can't have missed it. The domestic garden has become the focus of British outdoor life in the 1980s and 1990s, changing from something you once dug, mowed and pottered about in to something you now furnish and spend time in as if it were another room of the house.
Annual spending on garden furniture in Britain rose from pounds 55m in 1986 to pounds 187m in 1994, according to figures from Verdict Research, the market research company. Mintel commented earlier this year: "A series of warm and dry summers has prompted increased use of the garden as a leisure and entertainment centre and thus encouraged outdoor living. The barbecue concept is ideally placed to benefit from such a trend."
Too right. Throw another burger on the barbie, baby - between 1990 and 1994 alone British barbecue sales increased by 18 per cent. In 1987 pounds 22.7m was spent on barbecues; this year it is estimated pounds 43.6m will be spent.
Dr Sonia Livingstone, lecturer in social psychology at the London School of Economics, agreed that weather could affect lifestyle, but thought that the changes of the last 15 years could be put down to mass consumerism.
"The difference is, now when we have hot weather, we know what to do with it." she said. "With barbecues it is something that has spread around the world, a lifestyle we're importing. Twenty years ago we didn't see anything like Home and Away's beach culture; it came out of the blue.
"Before, the British personality was constructed in Britain and we never went out of it. Now we can buy into different personalities - not only walking-in-the-Lake District sort of people, but sun-loving beach people as well."Reuse content