Superdry, best known for its coats and hoodies, has warned of weaker than expected profits, saying shoppers have not bought extra winter layers this year.
It now expects annual profits of between £55m and £70m - analysts had been expecting around £84m.
The announcement hit Superdry's shares and they closed more than 38% lower.
The company is considering closing stores as part of a cost cutting drive to save £50m by 2022.
"Superdry had a difficult first half, impacted by unseasonably warm weather across our major markets, a consumer economy that is increasingly discount driven and the issues we are addressing in product mix and range," said Euan Sutherland, Superdry's chief executive officer.
Underlying profit before tax almost halved in the first half of the year, to £12.9m.
The retailer is a third of the way through an 18-month strategy to re-energise the brand which includes introducing childrenswear and 100% organic cotton products.
Mr Sutherland said the firm's "over-reliance" on jackets and sweatshirts was partly to blame for flagging sales.
He will oversee an efficiency drive which will include reviewing the number and size of their stores, and exploring renegotiating rents between now and March 2019.
Superdry's shares were down by as much as 30% on Wednesday. They have lost more than 70% of their value this year.
Superdry became popular with teenagers by providing high quality sweatshirts and other casual wear with a Japanese-style branding. However it has been losing ground and was dubbed recently by the Financial Times as a brand "for cool dads".
"It is a brand that hit a trend in the UK several years ago," said Maria Malone, from the Manchester Fashion Institute. "Its customers are older, thirty plus, but the website features young models, this confuses the consumer."
The problem is that Superdry's products are neither high fashion nor very functional, and its style, reminiscent of American Classic or Gap, is ubiquitous, Ms Malone said.
According to fashion retail analyst, Kate Hardcastle, the brand has saturated the market and has suffered from discount retailers producing copycat versions,
"To stay fashionable and engage with a buyer a brand has to have an air of exclusivity about it," she said.
Superdry's founder Julian Dunkerton left the board in March. Since then he has criticised the retailer's strategy.
He said the company should focus on its core jackets and hoodies and offer a far wider range of variations online: "Superdry is a series of core products - stick with them and tweak them," he said.
As part of its new strategy Superdry has launched a "fast-fashion" range aimed at a "younger, more fashion-driven" customer. The range mimics online retailers in going from design to delivery to consumers in six weeks and is being marketed via social media.