Last week's winter storm delivered coal to retailers from Missouri to Maine.
Although they had only two weekends left to shop before Christmas, people stayed home Saturday, according to a ShopperTrak report issued Tuesday.
The number of shoppers at the nation's stores plunged 25.6 percent Dec.14 from a year earlier. Much of the falloff is attributed to the two to 18 inches of snow and ice that covered the Midwest and Northeast.
The firm estimated that brick-and-mortar retail sales were down just 5.4 percent year-over-year, however. Both sales and traffic fell, but shoppers who made it to stores bought more.
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The sales pace quickened after the storm passed, ShopperTrak said, and sales for the overall weekend were down just 1.5 percent versus the same weekend last year.
"Looks like some shoppers got a jump on things when they heard the weather reports and got their shopping done on Friday before the weather set in," ShopperTrak said. "Friday sales were up 3.3 [percent]. Sunday sales were basically flat [-0.8 percent], which probably wasn't too bad since some shoppers may have stayed home to avoid the snow and cold that remained."
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Shoppers are going to malls and stores with a purpose, knowing what and where they want to buy, according to ShopperTrak. They window-shop ahead of time online, the firm said, so retailers should be adopting strategies to seize the opportunity, both before and once the shopper is in-store with the intent to buy.
So the big question that has retailers' white-knuckling it in the final days leading up to Christmas is: are those sales lost for good, or will shoppers hit the stores to finish up this week?
Retailers like having shoppers in stores because it provides a chance to persuade them to make unplanned purchases. The more harried and rushed shoppers feel, the less likely they are to veer from their shopping list.
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Still, some of the busiest shopping days of the season remain, said ShopperTrak. It predicts four of the top 10 sales days occur between now and Christmas Day.
Retailers are banking on it.
Some shoppers may have other plans, however.
According to the National Retail Federation's latest holiday survey, conducted by Prosper Insights & Analytics, nearly half of holiday shoppers indicate that they plan to do the rest of their holiday shopping online, the highest percentage in the survey's 11-year history.
As of Dec. 9, 32 million holiday shoppers had not even started shopping, the retail industry trade group said.
"Last-minute shoppers don't have quite the breathing room they did last year, when there were four full weekends, but we shouldn't underestimate procrastinators," said Pam Goodfellow, Prosper's director of consumer insights.
—By CNBC's Courtney Reagan. Follow her on Twitter