The International Council of Shopping Centers said chain store sales dropped 0.3 percent week-to-week, but rose 2.4 percent compared to the same week of 2011.
The group said overall traffic was weaker in the past week compared to the same period a year earlier.
Traffic was especially slow at discount and department stores, ICSC said.
Weather Trends International said the average temperature for the week was slightly cooler -- 1.2 degrees Fahrenheit -- than the same week a year earlier, but 1.1 degrees warmer than normal.
"Weather patterns indicate that demand in fall apparel would be "strongest in the Northeast ... with a plus 5 percent to plus 15 percent lift in demand over the last year while much of the rest of the nation will have seen demand flat," WTI said.
Also influential in the retail scene, for the second consecutive week the average national price of a gallon of gasoline fell. The price dropped 2.2 cents to $3.804 per gallon in the week that ended Monday, the U.S. Energy Information Administration said.