This seasonally-adjusted leap in sales volumes, unveiled yesterday by the Office for National Statistics, was nearly twice the 0.6% increase which had been forecast by the City and the third consecutive monthly rise. It was achieved in spite of a 0.3% month-on-month fall in non-food store sales.
The ONS said that feedback from supermarkets suggested that the sunny weather boosted sales across a range of products including food, alcohol, clothing, and outdoor items. Food store sales jumped by 2.5% month-on-month in July.
The fall in non-food volumes resulted partly from a 1.6% month-on-month tumble in sales in the "non-specialised" category, which takes in department stores.
Retail sales volumes in July were up 3% on the same month of 2012 - the sharpest year-on-year increase since January 2011.
Martin Beck, UK economist at consultancy Capital Economics, said the rise in sales volumes in July was a further promising sign that a consumer resurgence is in progress.
However, he added: "The pattern of sales suggests the sunny weather played an important role in driving purchases. And, while the boost from the good weather will fade, the drag from falling real earnings will persist."
Mr Beck conceded that, with a run of good economic news likely to support consumer confidence further and continued growth in employment, the retail sector looked set fair for the third quarter, even as the boost from the weather faded.
But he added: "With real pay set to continue falling into next year and households eating into their savings, the resources to sustain growth in sales still look lacking."
Peter Saville, partner at advisory and restructuring firm Zolfo Cooper, said: "The picture on the ground remains mixed, with many high streets and companies still struggling."