Promotions and discounts offered by U.S. retailers drove a 2.7 percent rise in holiday season sales despite six fewer days and a cold snap that kept shoppers from stores, retail industry tracker ShopperTrak said.

Reflecting a recovering U.S. economy, retail sales between Thanksgiving and Christmas rose for the fourth consecutive year, even though the number of people walking into stores fell 14.6 percent in the period, ShopperTrak said.

"It's a result of more and more technology in the hands of the consumer, which allows them to virtually window-shop," ShopperTrak founder Bill Martin told Reuters.

Retailers had only 25 holiday days to woo shoppers last year, compared with 31 days a year earlier, a difference that prompted stores to offer more promotions than usual earlier in the season.

As a result, retailers had a strong November. They also benefited from strong sales in the last few days of the year, Martin said.

"Consumers took a break from shopping after Thanksgiving weekend, so retailers were pressured to offer deep discounts and promotions in the final week before Christmas to finish the holiday on a positive note," Martin said.

Many shoppers went online to make purchases, particularly during a spell of abnormally cold weather in many parts of the United States during the first two weekends of December.

U.S. online retail spending rose 10 percent to $46.5 billion in the November-December 2013 holiday season, according to comScore. This was below the 14 percent growth that the data firm had forecast.

ShopperTrak said shoppers spent $265.9 billion during the latest holiday period. The increase was slightly ahead of the 2.4 percent jump it had forecast in September.

ShopperTrak had forecast a 1.4 percent decline in shopper traffic.

Retail sales rose 3.0 percent and foot traffic declined 16.3 percent in the 2012 holiday season.

Department store chain J.C. Penney Co. Inc. said on Wednesday that it was "pleased with its performance" during the holiday period, but the company's shares fell 8 percent in early trading after it reaffirmed its fourth-quarter outlook.

ShopperTrak estimated on Wednesday that U.S. retail sales would rise 2.8 percent in the first quarter of 2014, while shopper traffic would fall 9 percent.