Hallenstein Glasson expects to report a 20% drop in first half profit if current trends persist.
The clothing retailer says group sales for the first 14 weeks of its current financial year are down 7% on the same period last year, with August and September being particularly challenging.
The company says although its major trading months are still ahead of it, the slow start to the summer season means it is unlikely to match last year's first half result.
Hallenstein Glasson says net profit for the six months ending 1 February is likely to be about $8 million, compared with $10.4 million in the same period a year earlier.
If trading in the next couple of months turns out as the company expects, it will be the second poor half-year in a row the retailer has experienced.
Its net profit in the six months ended 1 August fell 31% to $8.3 million, dragging the full-year result down 11% to $18.7 million.
The result in the previous first half was a 6% improvement on the six months ended February 2012.