Memorial Day weekend sales are expected to be biggest ever, according to two surveys by America's Research Group (ARG).

Britt Beemer, chairman and founder of ARG, known for his Christian retail channel studies, estimated that shopping levels will exceed 35% compared to 2011.

"Spending levels will depend on the sale offers and the discounts when shoppers get into the stores," he said. "Those retailers who offer early-bird specials and open early on Memorial Day—yes, a la Black Friday—will see the best sales and the highest spending levels. The closer you come to creating Black Friday, the better your sales will be."

Two ARG surveys in late March and late April found that the number of Americans delaying their shopping to Memorial Day weekend is at an all-time high. Just over 6% of shoppers in March and 21% in April reported that they are delaying their shopping plans until Memorial Day weekend. A year ago, less than 3% of shoppers in March and only 11% of shoppers in April waited until Memorial Day.

"For the first time, Memorial Day weekend is scheduled to be the biggest in our 33-year survey history," Beemer said.