NEW YORK (CNN/Money) - It was too dry. It was too wet. The snowstorm kept customers away. The thaw cut into Flexible Flyer sales. Blaming the weather is one of the great traditions of America's retailers.

Now it's the heat that's stifled sales, of course. Despite strong quarterly results on Monday from home-improvement retailer Lowe's, there are signs that with the mercury rising, customers' desire for new merchandise has evaporated. In its weekly sales call Monday, Wal-Mart (WMT: Research, Estimates), the nation's largest retailer, said that back-to-school-sales were "off to a slow start as warm weather has affected apparel sales," and that overall sales were near the low end of its expected range. (Fun fact: Wal-Mart accounted for over 9 percent of U.S. non-auto sales last year.)

Meantime, Federated (FD: Research, Estimates), which owns Macy's and Bloomingdale's, said that the first two weeks of August have been "very disappointing and are running below our plan." And in survey sponsored by Myvesta, a debt management service, people said they planned to spend 17.5 percent less on back-to-school items this year than they did in 2001.

"So far the numbers have been on the soft side this month -- that's true across almost the entire industry," said UBS Warburg retail analyst Linda Kristiansen. "Everybody is blaming the weather."

Let's hope that it really is the heat that's got sales wilting. If not, the sharp slowing the economy saw in July may have been something worse than an air pocket in the ascent to recovery. With business spending still flagging, a slowdown in consumer spending could send the economy back into recession.

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"The trends have been relatively soft," said Bank of Tokyo-Mitsubishi senior economist Mike Niemira. "Is it the pause that refreshes, or does it augur problems ahead?"

Bank of Tokyo-Mitsubishi's retail chain store index, based on weekly sales reports from leading retailers, has shown weakness since the beginning of last month. July's weakness may have been due to generous incentives from car makers siphoning off cash that might otherwise have gone to the mall. The sharp drop in the stock market (which has since found its legs again) probably didn't help, either. Economists had hoped sales would snap back this month, but so far that hasn't happened. For the week ended Aug. 17, the chain store index showed its slowest year-over-year growth -- an anemic 1.4 percent -- since the beginning of the year.

Although she's heard the excuse many times before, Kristiansen thinks the weather may actually have something to do with the way sales have slumped. It really has been hot this summer (particularly last week when, according to the National Weather Service's Climate Prediction Center, the population-weighted temperature was nearly 3 degrees above normal), and on her recent field trips Kristiansen saw racks of fall clothes languishing. At the same time, retailers have cut down inventories sharply, which makes for fewer clearance sales of the things people really want, like flip-flops and Slip 'N Slides.

There are some hopeful signs sales could pick up. A fresh round of mortgage refinance activity is putting money into people's pockets and fear for the economy spawned by last month's slide in stocks has likely been eased by the recent rally.

But even though Kristiansen feels in her gut that sales are going to come back, she also says that there's no surefire way to tell the difference between a brief sales slump and the beginning of a real slowdown. For now all we can do is watch, worry and hope that things get better.