The nation’s biggest chain stores posted the second consecutive month of weak sales results, underscoring their concerns that sales growth this holiday season could be the slowest in five years.

“Consumers are exerting a lot of caution,” said Mandy Putnam, vice president at TNS Retail Forward Inc., a Columbus, Ohio-based market research and consulting firm. “Even with the number of promotions breaking early right now, retailers are really going to have to work hard to get them into the stores this season.”

Many retailers blamed the weather for some of the shortfall, suggesting that an unusually warm October deterred shoppers from buying fall sweaters, fleece and coats.

“It’s going to be a heavy discounting holiday season,” said Chris Terry, an analyst at Hodges Capital Management, which owns Kohl’s and Costco among its $1.3 billion in assets under management. “Consumers are getting stretched. Discounts are going to be more widespread.”

Sales at chain stores opened at least a year rose 1.6 percent in October compared with the same month last year, and below the forecast of 2.4 percent growth put forth by the International Council of Shopping Centers. September sales rose 1.7 percent.

Consumer spending drives the economy, accounting for more than two-thirds of economic activity. If consumers stop spending, it’s “highly unlikely” that the U.S. will be able to avoid a recession, said Scott Hoyt, director of consumer economics at Moody’s Economy.com in West Chester, Pa.

“Clearly the economy is in a more uncertain position and there are fears of a recession we haven’t had in a few years,” said Hoyt. “Therefore you want to watch the biggest piece of the economy very carefully.”

Wal-Mart Stores Inc., the world’s largest retailer, eked out a 0.4 percent sales increase by getting a jump on the holiday with early discounts on toys and electronics. Midtier department stores and mall-based specialty stores fared poorly, posting across-the-board declines. The lone standouts were luxury department stores.

Same-store sales fell 3.8 percent at Kohl’s Corp., 1.8 percent at J.C. Penney Corp. and 1.5 percent at Macy’s Inc. Even Nordstrom Inc., which had been largely untouched by the slowdown thanks to its upscale slant, saw its same-store sales fall 2.4 percent.

Among specialty stores, same-store sales were even more disappointing, falling 8.0 percent at Gap Inc., 6.0 percent at Limited Brands Inc., 4.2 percent at AnnTaylor Stores Corp. and 10.6 percent at Chico’s FAS Inc.

Stores that attract affluent shoppers outperformed in large measure the rest of the industry. Same-stores sales rose 8.5 percent at Neiman Marcus Group Inc., 10.6 percent at Saks Inc. and 9.0 percent at Costco Cos. Inc.

Target Corp., the discounter that caters to a higher-income shopper than rival Wal-Mart, reported a 3.9 percent same-store sales gain but warned investors that its stores are experiencing “soft sales in our higher-margin categories.”

Same-store sales measure sales at stores open at least one year and are a closely watched measure of a retailer’s health. Retailers typically generate 20 percent to 25 percent of their annual sales in November and December.

Wal-Mart, Target and J.C. Penney forecast that same-store sales will increase in the low single digits in November.

So far consumers have managed to continue to spend even as the housing and credit markets tumble. But economists are watching this holiday closely to see if consumer behavior changes.