NEW YORK (CNN/Money) - U.S. retail chains Thursday logged better-than-expected August sales, helped by a strong back-to-school season and summer clearances.

Discounters Wal-Mart and Target both beat their sales forecasts for the month.

Wal-Mart (WMT: Research, Estimates), the world's largest retailer, said August sales rose 6.9 percent. The company last week raised its forecast to a 4 to 6 percent gain for the month. It previously expected sales growth of 3 to 5 percent.

Net sales in the four-week period ended Aug. 29 were $19.5 billion, up 13.7 percent over the same period a year ago. Men's apparel, electronics, toys, hardware, intimate apparel and food were the strongest performing categories.

Wal-Mart said it expects September same-store sales to grow in the 3 to 5 percent range. In a pre-recorded sales update, it said its sales forecast was reduced from the August performance because it anticipates tax credit checks to have less of an impact and sees higher gas prices cutting into consumer spending.

The retailer last year logged a 3.3 percent same-store sales increase in September.

Warmer weather and school shopping boosted Target Corp.'s (TGT: Research, Estimates) August sales to 5.7 percent, above its earlier guidance of a 4 to 5 percent increase.

Sales at department stores, which have suffered the most in the overall industry downtrend, also got a lift.

Sears, Roebuck and Co (S: Research, Estimates). finally snapped a 23 consecutive month sales decline, posting a 3.9 percent gain in August, bolstered by strong demand for home appliances. Sears posted an 11 percent decline last year. The company anticipates September sales to be little changed from a year ago.

J.C. Penney's (JCP: Research, Estimates) August sales rose 6.5 percent, although sales at its Eckerd drug store division continued to disappoint with a 0.4 percent decline. The company said it expects September sales at its department stores to increase in the low-single digits in September.

Analysts said retailers benefited from easier comparisons, tax credit checks and reduced tax withholding.

"The back-to-school season started with a bang and we're expecting robust sales in September because the consumer appeared to be flooded with cash," said Bill Dreher, retail analyst with Deutsche Bank Securities.

"Back-to-school historically is a decent barometer for the holiday shopping season," Dreher added. "While we don't expect the sales momentum to maintain this pace, but we clearly expect retailers to leverage the topline growth for the rest of the year."

However, apparel chains were a mixed bag.

Specialty stores catering to teens delivered the best performance. Casual apparel retailer Pacific Sunwear (PSUN: Research, Estimates) logged a 15.6 percent gain in August, driven by back-to-school momentum, while Hot Topic (HOTT: Research, Estimates) posted an 11.8 percent jump last month.

But Abercrombie & Fitch (ANF: Research, Estimates) disappointed with an 11 percent sales decline, while Gap said its results were weaker than expected.

"There's very little excuse for anyone posting weak sales right now," Dreher said. "If that is happening, it because of company specific excuses. The macro environment overall is very strong. The first month of the quarter got a stellar start and that usually put a lock on the rest of the quarter. Retailers should post improved earnings going forward."

However, Kurt Barnard, independent retail consultant, said he's not convinced of a turnaround.

"All we saw in August was a celebration of the discounters," said Barnard. "The department stores had very few standouts and the apparel group mostly did terrible. Consumers are still not buying the product, they're buying the pricetag and that's why we're seeing a big gravitation to discount stores."