The new figures - the best on the high street for four years - add weight to recent signs that business confidence is returning.
The Scottish Retail Consortium's retail sales monitor has reported that total sales were up 3.5% last month compared with the same period last year.
The food sector saw the largest increase, at 3.6%, but sales of non-food, including those of fashion retailers and garden centres, also took advantage of the summer sun in what is thought to have been the hottest August since 2004.
The numbers follow an even stronger July, which saw record temperatures and Andy Murray's Wimbledon success led to a rise of 4% compared with July last year.
The encouraging figures come in the same week that the Bank of Scotland's purchasing managers' index showed the recovery was picking up speed and Chancellor George Osborne insisted the economy was finally turning a corner.
SRC director Fiona Moriarty said: "The best August since 2009 has helped to keep the positive momentum going following a record-breaking July.
"Combined with a recent uplift in Scottish consumer confidence, the signs are that many of us are increasingly feeling more optimistic about the economy and responding well to retailers' targeted promotions and new ranges."
She said food sales were boosted by picnics and barbecues while the return to school had helped childrenswear.
The figures also revealed the Scottish total sales growth for August sat only marginally behind the UK figure, of 3.6%.
The average for total sales growth for the last three months is now said to be in line with the UK, at 3.4%.
Like-for-like sales, which take out factors such as new store openings, were 0.8% higher last month across all categories compared with 12 months ago.
David McCorquodale, the Edinburgh-based head of accountancy firm KPMG, said the "welcome warmth" of summer continued to stoke the tills on the high street last month.
He said: "Fashion retailers and garden centres benefited from the weather but the surprise package was the uplift in sales of furniture and flooring which, due to its higher ticket price, gives the strongest indication of returning consumer confidence."
Garry Clark, head of policy and public affairs at the Scottish Chambers of Commerce, said there was still more to be done for economic growth.
He said: "These figures suggest a continuing improvement in levels of consumer confidence and stand as further evidence that there are more positive than negative signs in the Scottish economy.
"Increased sales are good news for Scotland's retail sector, which has experienced a very promising summer.
"However, there remains a long way to go before our economy can be said to be firmly back on the road towards sustained growth."
Major shopping centres in Glasgow, Edinburgh and Aberdeen all reported strong sales with some suggesting it was a good indication for the upcoming Christmas trading period.
l Vince Cable will today attack economic "complacency" in what will be widely viewed as a staunch criticism of Mr Osborne.
The Liberal Democrat Business Secretary will also suggest that the UK's economic recovery is yet to be "meaningful".
Mr Cable is expected to say: "The kind of growth we want won't simply emerge of its own volition.
"In fact, I see a number of dangers. One is complacency, generated by a few quarters of good economic data.
"Recovery will not be meaningful until we see strong and sustained business investment."