The group, which owns the HMV and Waterstones brands, says it expects a strong Christmas, with several blockbuster DVD releases, high-profile music releases such as the new Take That album, and major book launches.
But it said the weather had been a problem at the start of the Christmas shopping period.
The group's turnover fell by 6% in the six months to 23 October, with sales in the UK and Ireland falling 15.3%, leading to a pre-tax loss of £41.3m.
This compares with a pre-tax loss of £24.9m in the same period last year.
The group says final year performance will be dependent on Christmas, which accounts for 60% of the group's trade.
A company financial update stated: "Despite more encouraging trading at the beginning of the second half, the start to the Christmas trading period has been undermined by the severe weather of the last two weeks, which has significantly affected consumer footfall and consequently makes trading patterns hard to determine at this stage."
Simon Fox, chief executive of HMV, said: "The increased seasonal loss reflects the tough trading conditions in HMV UK, where good progress in growing new product categories was not sufficient to offset weak entertainment markets.
"In Waterstone's, the recovery plan is on track, and in all businesses we are very well prepared for the important weeks ahead, with a strong line-up of offers across all product categories and a focus on delivering high quality service both in-store and online."
HMV appointed in August, and the group has been diversifying into , , and .
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