ly issued by Thomson Reuters on Monday found that analysts expect the 25 retailers in its index -- including Costco Wholesale Corp, <COST.O> Target Corp <TGT.N> J.C. Penney Co Inc <JCP.N> and Saks Inc <SKS.N> -- to report a 4.7 percent increase in August sales at stores open at least a year, a measure known as same-store sales. The chains that report monthly sales represent only about 10 percent of retailers, and the storm affected roughly 15 percent of the U.S. population, said Craig Johnson, president of Customer Growth Partners, who lost power at his Connecticut home early on Sunday. "There will be a few retailers that will use the hurricane as an excuse for poor performance, but these are some of the same people who have been performing poorly for months now," he said. "Gap's numbers are going to be lousy this month, Aeropostale's will not be good, but they were bad before the storm." AUTO SALES UP -- AND DOWN As much as a fifth of U.S. auto sales are often generated in states affected by Irene, said Paul Taylor, chief economist with the National Automotive Dealers Association. And in those states, August sales will likely be down about 10 percent. A bigger problem related to Irene may hurt September sales as well, Taylor said. "The real issue is going to be flooding," he said. The average forecast of 44 economists surveyed by Reuters was 12.1 million vehicles were sold on an annualized basis, up from 11.5 million a year ago, but off slightly from 12.2 million in July. Honda appears to be struggling the most. Edmunds.com and TrueCar.com expect Honda's sales for August to drop at least 22 percent to 25 percent from last August, and for Toyota's sales to fall at least 11 percent to 14 percent. They show General Motors Co <GM.N> August sales up 20 percent, Ford Motor Co <F.N> up 12 percent to 14 percent, Chrysler Group LLC up 21 percent to 22 percent and Nissan Motor Co <7201.T> up 16 percent to 22 percent. Chrysler is under the management of Italy's Fiat SpA <FIA.MI>. SCHOOL DAZE Retailers that sell back-to-school items likely felt Irene's pinch as the storm essentially shut down malls on a weekend when parents normally shop for clothes and notebooks, not bottled water and flashlights. "This is a major weekend of sales that were planned, but that won't happen, in one of the most densely populated regions," said Joel Bines, a managing director of consulting firm AlixPartners. The damage could take 1 percentage point off August same-store sales, said Bines, adding that leftover merchandise will likely be discounted, damaging gross margins.