NEW YORK (CNN/Money) - Wal-Mart Stores Inc. cut its August sales forecast Monday, saying it expects sales at stores open at least a year to be flat to up 2 percent, citing weak back-to-school trends and hurricanes that forced it to close up to 75 stores.

Wal-Mart had been forecasting that sales at stores open at least a year, known as same-store sales, would rise 2 to 4 percent for the month.

Wal-Mart (WMT: down $1.19 to $53.46, Research, Estimates) stock fell about 2 percent in morning trading on the New York Stock Exchange.

In a pre-recorded weekly sales update, the world's largest retailer said back-to-school sales were falling below expectations.

The company said sales last week were also hurt from closing up to 75 stores due to hurricanes in parts of the country. The retailer estimates that 200 stores in all had been affected due to the weather.

Additionally, Wal-Mart said the fading stimulus from last year's child tax credit checks, the shift of the Labor Day holiday by one week, reduced clearance activity and tougher comparisons were all factors dampening August sales.

Among its better-performing categories last week were food, paper products and pet supplies, it said.