Sales dropped 2.3 percent week to week although they were up 3.8 percent compared with the same week of 2010, the International Council of Shopping Centers said.
"Again this year, the post-Thanksgiving/Black Friday lull has set in," ICSC said.
Weather Trends International tracked national average temperatures 3.4 degrees Fahrenheit warmer than the same week a year earlier, which makes shopping comparatively comfortable, but fails to spur sales of seasonal items.
Gasoline prices were favorable for retailers, dropping to an average $3.29 per gallon on Dec. 5, the Energy Information Agency said.
It is possible Black Friday sales simply took the wind out of the retail sector, because consumers are getting their holiday shopping done early.
In a weekly, pre-holiday survey, 56.9 percent of respondents indicated their holiday shopping was done. In the same week of 2010, 50.1 percent indicated they had finished their holiday shopping, a significant difference, ICSC said.