Retailers are building up to one of the most crucial weekends of the year as shoppers are expected to flock to the grocers in search of party food to celebrate the Queen’s Diamond Jubilee.

Moneysupermarket.com has estimated that weekend spend will come in at £823m, far outstripping the uplift of £480m attributed to the Royal Wedding weekend last year and providing a welcome fillip to consumer spending.

The major grocers are battling hard for spend using promotions and in-store merchandising to get consumers in the mood to splash out on party food.

Each are taking different tactics, with Asda offering £5 off shoppers’ next £40 shop while Sainsbury’s is offering a platter ordering service to allow customers to pick up ready-to-eat party plates of food.

Those with smaller market share, including Iceland and Waitrose, are also likely to thrive given their traditional strength in party and barbecue food.

But will the spending be confined to food? “Whatever the weather, food spend is likely to go up due to parties and the two day bank holiday, but non-food is more uncertain,” says Sarah Peters, lead retail analyst at Verdict.

“If the weather is good then people will go out and buy new clothes. DIY and garden retailers are also heavily weather dependent – if the weather is good then they could see a real sales spike.”

The division of spend is also interesting. The high street is likely to enjoy the bulk of the spending, according to Peters, with shoppers looking to do last minute top-up shops and enjoy the sunshine, socialising outdoors rather than in indoor shopping centres.

Meanwhile, some commentators have questioned whether people will go shopping over a weekend likely to be busy with parties or spent at home.

Retailers should also take a step back and note that, despite the expected sales fillip, the Jubilee weekend comes after six weeks of dreadful weather that drove customers away from the shops.

Data released by the Office for National Statistics last week reveals sales growth cooled in April to their slowest rate for two years, while sales volumes dropped 1.1% compared to last April – the largest fall in sales volumes year on year since August 2011.

Retailers will largely be focussed on recouping lost sales over the weekend, rather than driving new growth.

However the final numbers pan out, the Jubilee, European Championships and the Olympics will still offer an unprecedented opportunity to build ‘Brand Britain’, improve consumer sentiment and educate visiting consumers about the British retail brands which also exist in tourists’ home countries.

But, as with everything in the UK, the weather remains an important, but unpredictable, vital cog at the centre of one of the most crucial periods of 2012.