The Autumn heatwave knocked John Lewis's sales in the week to 1st October.
They were down 7.9% on last year, as shoppers stayed away to enjoy the sun.
Household budgets are under strain anyway so some will take John Lewis's "tough week" as a warning sign.
The department store chain said trade in the electrical, home and technology areas stuttered due to the impact of the weather.
Sales of autumn fashions were hit as well, though John Lewis is hoping that more people will grace its doors now that cold winds are starting to blow.