WASHINGTON, July 27 (UPI) -- The summer's streak of hot weather sales for U.S. retailers may turn against stores in August, a retail group said Tuesday.

U.S. retail sales rose 0.6 percent in the week ending last Saturday and posted strong gains over the same week a year ago, said the International Council of Shopping Centers.

The group said sales rose 3.8 percent compared with 12 months ago, continuing a trend of increased sales due to a summer consistently warmer than 2009.

"Easy comparisons continue to lift sales while abnormally hot weather helped drove some customer traffic in regions," the trade group said.

Retailers, meanwhile, are in between summer clearance sales and the busy back-to-school season, "which makes it difficult for retailers to leverage the hot-weather for sales," the ICSC said.

Meanwhile, many states promote back-to-school sales with tax-free holidays in late July or early August, the first occurring in Mississippi on July 30-31. Summer weather now could work against the retail sector as "lingering hot weather may likely delay the launch of the consumers' back-to-school spending," the group said.