No wonder retailers, large and small, are groaning.

At Polly-t, a tiny boutique in Central, sales have halved compared to last year. With the mercury still hovering above 20 degrees Celsius, owner Polly Tang Kam-kwan complains that most of her regulars haven't been making their usual purchases, leaving her third-floor store in Stanley Street crammed with unsold stock.

'No one wants to buy winter items like wool scarves and cardigans, or cashmere jackets yet. I have HK$300,000 locked in the stock,' she says.

With the next season's inventory expected to arrive within weeks, Tang will struggle to squeeze it into her shop. Rather than set a precedent by giving huge discounts, she says she may donate some clothes to charity to make space for new stock.

According to the Hong Kong Observatory, the past two months have been unusually warm. Mean temperatures in October averaged 26.4 degrees Celsius - the hottest since 1983; last month's mean was 23.3 - two higher than the 30-year average. And despite a few chilly nights, this month promises more warm weather.

Indeed, going by meteorologists' forecasts, residents may eventually be giving away most of their winter gear as worsening global warming and urban build-up are set to end meaningful periods of cold weather.

The loss of winter will put a dent in the fashion business. Shoppers are generally willing to dig deeper for winter attire, which feature more designs and are embellished with more details. Winter is usually the most lucrative season for fashion, says Edmund Yip Kwan-wang, a designer for local fashion firm PMTD. 'In cold weather, people wear more layers and accessories such as scarves and gloves,' he says. 'But in other seasons, the weather in Hong Kong is warm enough to wear a top with pants or skirts.'

This year the company, which operates more than 30 outlets under its five youth-oriented brands - 2%, +-??, TH:, WIP and ODF - was struck hard by the unseasonable weather. Having enjoyed great success with its winter lines last year, the company decided to make more this season. But demand has shrivelled in the warmth, with sales falling by a quarter this season.

'Our warehouses are so stuffed with unsold winter wear that some staff members are complaining there's no room to walk through,' says PMTD press officer Molly Law Oi-yu.

Sluggish business forced PMTD to start seasonal discounts two weeks ago, much earlier than usual. 'The fashion world is a cruel one. Designs which are all the rage this season may soon become outdated, so we need to sell the items while they are still in,' Law says.

Fortunately, like other big chains, PMTD can offload some of its surplus to sales networks outside Hong Kong; the company exports to overseas partners and operates 100 outlets on the mainland.

The company may switch to making more perennial designs for Hong Kong to cope with the disappearing winter - but there is a drawback. 'People don't shop as much if it's something to wear all year round,' Law says.

'But it is hard to depend on the Hong Kong market. My boss jokes that Hong Kong may no longer have four seasons and we only need to design clothes for one climate.'

Environmentalists and weathermen blame poor urban planning and energy use for exacerbating the greenhouse effect in Hong Kong. While average global temperatures have risen by 0.6 degrees Celsius in the past century, it's risen by double that figure in Hong Kong. Worse, the heat-up rate is quickening to 6 degrees per 100 years.

Cheng Luk-ki, head of scientific research with environment group Green Power, says the forest of high-rises are built too closely together, obstructing wind flow and trapping hot air. Inefficient building design and extensive use of heat-absorbing materials such as concrete and glass further raise ambient temperatures. And the city's heavy traffic, excessive lighting and reliance on air conditioners worsen matters.

Many families set their air conditioners to high to enjoy hot-pot or snuggle in bed under a quilt at the height of summer, Cheng says, while shops set indoor temperatures at similarly chilly levels.

But Cheng says residents fail to realise that air conditioners are pumping heat into the surrounding streets. 'It is a vicious cycle,' he says. 'Hong Kong people have been enjoying today's comfort at the expense of the future.'

Meanwhile, casual wear chain Chevignon is changing its production plans to accommodate the altered state in Hong Kong: it has slashed production of heavy clothing for the market since last year.

Chevignon merchandiser Chan Ping-ping says the firm has halved its stock made with wool and down and, instead, is designing more year-round items such as sweat- shirts and thin jackets. 'Of course, jeans remain our major product, which is something you can wear in any weather,' he says.

But green activists argue that the city environment doesn't have to be this way. Minor lifestyle adjustments can bring significant changes to the micro-climate, Cheng says.

More judicious use of lights, air conditioners and electrical devices - all of which generate heat - will help, as will weaning drivers off their habit of keeping engines (and air conditioners) idling while waiting. Even steaming food instead of stir-frying makes a difference, Cheng says. 'To create steam, water is only heated to 100 degrees Celsius, but temperatures can be really high for stir-fries,' he says. Plus it's a healthier way to cook.

Hong Kong people can ignore the environmental warning signs and simply turn up the air conditioners to put on their winter fashions. 'But do we really want to do away with the seasons?' Cheng says.