Updated from 10:34 a.m. EDT

Hurricane devastation, high gas prices and unusually warm weather cut into discretionary spending for low- and middle-income consumers in September, but given all the obstacles, retail chains turned in better-than-expected results.

Ken Perkins, president of industry tracker Retail Metrics, said his firm's survey of about 100 national retail chains turned up an aggregate same-store sales gain of 4.1% for the month. The result beat expectations for a 3.6% increase.

Same-store sales serve as a key measure of a retailer's performance, covering sales at locations that have been open for at least one year.

Retail Metrics reported that 63% of retailers in its index beat expectations, well above the long-term average of 54%, while just 35% turned in negative surprises, below the long-term average of 42%.

High-end retailers like Neiman Marcus ( NMG.A) remained strong, while teen clothing chains including American Eagle Outfitters ( AEOS) and Aeropostale ( ARO) were mixed.

"In a broad sense, this looks like more of the same, but the reality is that these September numbers look a bit more uneven and a bit more noisy than numbers in past months," said Michael Niemera, chief economist and director of research with the International Council of Shopping Centers.

"The numbers may overstate the performance," he continued. "Discounters got a nice lift from the 50% increase in gas prices, which inflated their results, but there is downside to those gas prices because they cut into demand."

Following the chain-store reports, the sector was stronger. The S&P Retail Index was recently gaining 0.9%, and the Dow Jones U.S. Retail Index was higher by 0.4%.

Still, a spate of retailers lowered expectations for earnings in the second half of the year, and the reports failed to quell concerns about a slowdown in consumer spending.

The world's largest retailer, Wal-Mart ( WMT), said its same-store sales were in line with estimates, rising 3.8% last month. The company's Wal-Mart stores posted a 2.6% comp-sales increase, while its Sam's Club wholesale clubs recorded 9.8% growth. Total sales rose 9.7% to $28.24 billion.

On the front lines of the hurricane relief effort along the Gulf Coast, the retailing giant had closed 126 locations due to Hurricane Katrina and 155 because of Hurricane Rita, but by the beginning of October, only 15 stores remained closed.

Meanwhile, gasoline sales provided a nice cushion for Wal-Mart. Excluding gasoline sales, Sam's same-store sales would have risen 6.3%, and total comparable sales would have grown 3.2%.

The retailer also saw increased sales of canned foods, water, candles, batteries, flashlights and lanterns as consumers prepared for the storms. Afterward it benefited from a pick-up in basic apparel, hardware and cleaning supplies as residents of the storm-ravaged region started their recovery.

As for its third-quarter results, Wal-Mart said the hurricanes would reduce earnings by 1 cent a share, but the company maintained its forecast for a profit of 55 cents to 59 cents for the period.

Wal-Mart's chief competitor Target ( TGT) beat analysts' estimates with a 5.6% jump in September comps. Total sales were up 11.4% to $4.31 billion, and the company reaffirmed its earnings guidance, forecasting a profit of $1.50 a share for the second half of the year.

Elsewhere in discount retailing, Costco ( COST) also got a lift from gas sales, reporting an 11% increase in September comps. Net sales for the month added 13% to $5.14 billion.

Costco said its fourth-quarter earnings jumped 20% on increased sales and lower taxes, while its board approved a new $1 billion stock buyback plan. Net income totaled $354.7 million, or 73 cents a share, compared with $296.8 million, or 62 cents a share, logged in the same quarter last year. Excluding a tax benefit, the company would have earned 66 cents a share, edging out Wall Street's expectations by 2 cents.

Also, BJ's Wholesale Club ( BJ) came up short of expectations, with September same-store sales climbing 3.8%. Total sales rose 8.7% to $735.9 million.

As for department stores, Federated ( FD) reported a 1.3% rise in September comps, beating analysts' estimates. Total sales skyrocketed 89.6% for the month to $2.58 billion, thanks to its recently completed acquisition of May Department Stores.

Federated, the parent of Macy's and Bloomingdale's, also set its profit targets for the rest of the year. The company expects earnings from continuing operations of $1.50 to $1.65 a share in the third quarter and $2 to $2.20 a share in the fourth quarter. Shares were selling off in premarket trading, recently down $2.46, or 3.9%, to $61.15.

J.C. Penney's ( JCP) September comps were up 1.4%, coming in just short of expectations. Total department-store sales rose 1.9% to $1.25 billion, while catalog and Internet sales were up 0.4%.

Talbots ( TLB) said its same-store sales dropped 5.1% in September, disappointing investors who were expecting a gain. The company also cut its third-quarter profit forecast.

On the upper end of the spending spectrum, Neiman Marcus beat estimates on a 9.6% comparable-sales gain. Total September sales rose 9.2% to $397 million.

Nordstrom ( JWN) said its same-store sales increased 4.1% for the month with total sales up 6% to $636.7 million.

Apparel retailer Gap ( GPS) saw its same-store sales fall 6% in September, but analysts were expecting a bigger decline. Limited ( LTD) logged a 2% drop, in line with expectations.

Teen clothing chains, a longtime retail favorite on Wall Street, posted varied results. On the upside, American Eagle said its same-store sales for the month rose 13%, beating expectations. Total sales climbed 20.9% to $183.8 million.

The retailer also affirmed its third-quarter earnings guidance, predicting a profit of 43 cents to 44 cents a share. That would mark an increase from last year's third-quarter earnings of 39 cents a share.

Also, results from Abercrombie & Fitch ( ANF) surged past expectations with a 21% comp-sales gain for the month.

Another company in the sector, Aeropostale, disappointed investors with a same-store sales drop of 4.2%, Analysts were expecting a small gain. Total sales increased 15.1% to $104.3 million.

"While our sales trend started off strong at the beginning of the month, it decelerated as the month progressed due to an unexpectedly challenging retail environment," the retailer said in a statement. "Despite our healthy transaction levels, our average unit retail continues to be under pressure due to increased promotional activity. We continue to make progress on clearing through our excess inventory and are focused on positioning ourselves appropriately for the holiday selling season."

Based on the results, Aeropostale lowered its guidance for the third quarter, forecasting earnings of 45 cents to 48 cents a share. Analysts were expecting earnings of 50 cents a share, according to the consensus estimate carried by Thomson First Call.

Hot Topic ( HOTT) continued its losing streak, posting a decline in same-store sales of 5.6%. Total sales rose 8% to $62.5 million. The mall-based clothing chain geared toward the counter-culture set affirmed its third-quarter earnings estimate, expecting to log 15 cents to 18 cents a share.

"Overall, we've had a year-to-date performance by chain stores of 3.8% same-store sales over last year, and we expect more of the same going into the holiday season ," Niemera said. "We should be seeing stronger demand, but there are lots of things to worry about for retailers, starting with consumer fundamentals. They're not looking great going into the holiday, and on top of that, you have worries about home heating season set to begin with high prices and a cold winter expected."