SAN FRANCISCO -- Warm temperatures are getting the blame for potentially weak sales at chain stores in September, but the troubled economy isn't helping either.Most retailers will report their September sales data on Thursday morning, and overall expectations are low. Already, retail giants Target ( TGT) and Lowe's ( LOW) have warned of weaker-than-anticipated results for the period, and analysts expect the numbers to show the seventh straight month of slowing growth. According to Thomson Financial, the nation's top retailers are expected to post a collective 2.3% rise in September same-store sales, or sales at stores open at least a year. That's down sharply from a 6.3% increase last year. Those estimates exclude giant Wal-Mart ( WMT), which tends to skew results. When factoring in the world's largest retailer, the prediction for September sales growth falls slightly, to 2.1%, vs. a 4.2% increase last year. On Wall Street, the usual suspects --weather and economic worries -- are being held responsible for the drop. Kimberly Greenberger, an analyst for Citigroup, said she remains cautious on September sales as slowing consumer traffic, high gas prices and warm temperatures will likely crimp results. "We are most cautious on retailers with high levels of wintry apparel given warmer temperatures," she wrote in a research report, pointing specifically to J. Crew ( JCG) emphasizing coats and outwear; Children's Place ( PLCE) focusing on coats; and Pacific Sunwear ( PSUN) carrying a lot of fleece goods.