The back-to-school season is mission critical for retailers, since it ranks just behind the holidays in terms of sales. But thanks to unusually warm weather that has kept consumers from embracing a clothing frame of mind, apparel retailers, including Wal-Mart, are reporting sluggish sales.

Today, Wal-Mart Stores Inc. reported a same-store sales increase of 4-6% for the month through Aug. 23, which is in line with the Bentonville, Ark., company's projections. School supplies were among the strongest sellers, as was fashion apparel, but overall clothing sales were weak.

Federated Department Stores Inc. relayed gloomier news. The Macy’s and Bloomingdale’s parent company, based in Cincinnati, said today that same-store sales are expected to decline more than the 1-3% it had originally expected. Sales in the third week of August were, however, stronger than this time a year ago. Brisbane, Calif.-based Bebe Stores, a women’s apparel chain, has also cut its same-store sales forecast for the September quarter, and inventory levels are down.

J.C. Penney Co. Inc. is swimming against these tides, with department store sales doing better than anticipated — flat to slightly higher same-store sales were forecasted - with the support of back-to-school purchases. Fine jewelry and children’s and women’s apparel were the company’s strongest performers last week.

Moreover, and in Wal-Mart’s favor, membership income at Sam’s Club warehouse club stores were up double digits on a percentage basis.