Sales of charcoal soared 450%, Pimm's sales leapt 316% and it sold 262% more sun cream, helping the supermarket to a 16.8% sales surge in the week to July 6.
But department store chain John Lewis saw the reverse effect, with weekly sales up just 0.2%, as sunshine, Wimbledon tennis and Lions rugby kept shoppers away.
Waitrose's sales of £125.8 million were up on £109.8 million a year earlier, the best weekly takings outside Christmas and Easter. John Lewis's sales of £71.7 million edged up on £71.6 million a year earlier.
Sales of barbecue accessories were up 500% at Waitrose, barbecue meats leapt 173% and sales of prepared salads rose 75%. Cider sales were 140% higher and it sold 144% more ice cubes.
Andy Murray's progress at Wimbledon also sent sales of swingball sets soaring 596% from the start of the tournament. John Lewis saw a 300% increase in sales of fans and other cooling products, while home furniture sales were up 66%.
Matthew McCormack, fashion buying director at John Lewis, said the week "started stronger than it ended, with footfall dropping away on Saturday".
The retailers together form the employee-owned John Lewis Partnership, which saw an overall 8.9% weekly sales increase on a year earlier.
The figures follow a recent upbeat industry survey, which showed better weather lifted sales of clothing and footwear in June to give the beleaguered high street a welcome boost and add to growth prospects. Like-for-like retail sales rose 1.4% in June on a year earlier, following a 1.8% gain seen in May, the British Retail Consortium (BRC) said, raising hopes that a recovery in consumer spending can fuel the economy.