Total divisional sales (excluding fuel) at Waitrose were 4.2% higher than last year in the week to August 10.
Waitrose retail director Rob Collins said this was despite a tough comparison against the same week last year, which experienced exceptionally strong trade as the hotter weather and Olympic closing ceremony prompted shoppers to buy everything they needed for parties and alfresco gatherings.
The cooler weather at the beginning of the week saw customers return to eating habits more akin to the winter months, by stocking up on warming foods including Indian ready meals (up 17%), pasta (up 17%), stir fry mixes (up 12.5%)
Prepared vegetables and root vegetables were popular accompaniments, with sales up 11% and 9% respectively.
Shoppers also stocked their freezers with comfort foods including frozen pizzas, up 26%, and frozen chips and potatoes, up 11%.
During the period Waitrose opened the doors to its first branch at Aylesbury, in Buckinghamshire, and launched its new farm shop on the Leckford Estate in Hampshire.