American clothing retailers are facing their worst season for five years, with shopping centres caught out by unseasonably high temperatures in what should be the busiest shopping period of the year.

Last month the North East Coast of the United States recorded temperatures up to 5C above normal, according to Planalytics, a Pennsylvania-based weather consultancy.

September marks the beginning of the busiest retail season, with shoppers buying big-ticket clothing items such as coats, boots and heavier knit-wear before winter. However, America’s biggest clothing retailers and department store groups last week reported September sales at the lower end of Wall Street expectations. Like-for-like sales by Gap, owner of the Banana Republic chain, tumbled 7 per cent in September.

For Macy’s, the world’s biggest department store group, same-store sales fell 2.7 per cent – more than three times the rate of decline forecast by Wall Street analysts. A spokesman for Macy’s – which derives 85 per cent of its sales from clothing, shoes and accessories, such as cosmetics – insisted: “If the weather turns late, the sales start late. It’s part of the deal.”

America’s National Retail Federation predicted last month that sales would rise by only 4 per cent in November and December; it would be the worst performance since 2002.

Russell Jones, of Alix Partners, a consultancy, said: “Being out of sync’ with the weather is a far worse problem for retailers who are already having a tough time. In the case of Gap and Macy’s, they are already struggling to have a good reason for people to buy their merchandise.”

A spokesman for Gap said: “We focus on things we can control. Weather is not one of them. We have never commented specifically on the impact of the weather on sales.”

Mr Jones said that steps by retailers to have merchandise made in countries with lower labour costs, such as China, had reduced stores’ ability to alter clothing ranges at the last minute. He said: “Lead times for sourcing goods are much longer now – a retailer has to make commitments further in advance because of the shipping period. There is a seven-to-eight-week turnaround to get goods from a port in China into your store in the US.”

Although newer American retailers, such as Zara, still buy goods made in the US, most Gap merchandise is made outside America, Mr Jones said.

JC Penney, America’s third-biggest department store chain, admitted that like-for-like sales in September had fallen by 4.6 per cent and it cut its third-quarter profit forecast by 22 per cent. Target, the second-biggest discount chain in the US, said that its September sales were up 1.2 per cent - well below its already reduced forecast for a gain of 1.5 to 2.5 per cent.

The unseasonable weather patterns, in which New Yorkers sweltered in the 80s throughout September, could not have come at a more difficult time for clothing retailers. US retail sales have been slowing as Americans fret over the falling value of their homes in the worst housing recession for 16 years and as food and fuel costs rise. September US retail sales, excluding cars, food and petrol, rose only 0.1 per cent. A flat October would mark the worst three-month period since the invasion of Iraq in 2003.

Ian Shepherdson, of High Frequency Economics, commenting on last month’s retail sales, said: “Finally, cracks are appearing.”

Retail sales are watched by the US Federal Reserve as a snapshot of the economy’s health. About a third of US spending is retail. Another rate cut may depend on whether there is evidence that turmoil in financial markets has hit the wider economy, which could be expressed in retail sales data.