Why trudge through the snow and slush to find that perfect gift when you could order it from your couch, cup of cocoa in hand?
The second winter storm of the holiday season is making its way through the Midwest and toward the Northeast this weekend, dumping snow, ice and rain on shoppers just as the holiday crunch intensifies.
Experts said the storm will keep most shoppers indoors this weekend, taking a bite out of the already weak brick-and-mortar traffic seen this season. But while the wet weather and below-freezing temperatures will put off some shoppers—maybe even causing them to cut back on unnecessary purchases—large retailers with online operations will be able to salvage some sales because the blow will fall before free shipping offers expire.
(Read more: Let it snow: Determined shoppers will 'find a way')
"If historical patterns hold … we should see a pretty significant spike in online traffic," said Scott Bernhardt, president of Planalytics, a consulting firm that analyzes the effect of weather on consumer demand.
ComScore said there is typically more online spending in the first and fourth quarters, coinciding with the seasonally cold months. But it's difficult to gauge a particular storm's impact on Internet sales, said Andrew Lipsman, vice president of marketing and insights.
This storm will have the opposite effect on physical stores than the one that brought pre-Black Friday slush to much of the U.S. Then, the weather cleared before the critical holiday weekend, driving demand from those looking to get out of the house and enhance their winter wardrobes.
This severe weather occurs over an important shopping weekend. It's the latest challenge in a retail environment pressured by the lack of must-have toys and apparel, aggressive promotions and cautious spenders. Further, this year has one less weekend between Thanksgiving and Christmas, making every Saturday and Sunday especially crucial, experts said.
According to ShopperTrak predictions, Saturday and Sunday were expected to be this season's fourth- and eighth-busiest shopping days, respectively. Traffic the first week in December—generally a slower week—was down over 21 percent year over year.
"We're going into the season shorthanded because of time, and now Mother Nature is playing hardball," said Paul Walsh, chief meteorologist at The Weather Channel's WeatherFX. "For retailers, she's playing hardball below the belt."
The bright spot is that the storm is descending as many retailers are still offering free standard delivery. According to research by StellaService, companies including Amazon and J. Crew guarantee that such orders placed up to and through next week will arrive by Christmas, depending on the vendor.
That should benefit an already strong holiday season online, which posted its biggest Cyber Monday ever, ringing up sales of $1.74 billion, according to ComScore.
The storm will be particularly damaging to brick-and-mortar stores in the Northeast, which accounts for about 20 percent of the country's buying power, Walsh said.
And Bernhardt said that boutiques, particularly those without an online presence, stand to lose the most.
Some major retailers, including Gap, Sears, American Eagle and Kohl's, have about half of their stores in the storm's path, according to Planalytics. TJX also has 50 percent of its stores in the storm's crosshairs—a particular disadvantage as competitor Ross Stores has a sizable presence in the West.
Although the companies will recover a good portion of that business online, the industry as a whole is likely to lose sales of nonessential items—in particular, "gifts" that shoppers buy for themselves.
People start thinking about the things they don't really need, and it adds up quickly, according to Bernhardt.
"They don't get that one or two more things," he said. "That's significant."
Running out of excuses
Still, Walsh said, many retailers use bad weather as an excuse for poor sales. While storms do affect sales, technology enables retailers to leverage weather instead of being victimized by it—advertising items such as warm-weather apparel when temperatures drop, for example. This trend will only increase over the next five to 10 years, he said.
(Read more: No time for online: Shoppers rush to actual stores)
Weather's biggest impact on retail is reflected in what people buy, Walsh added. So far this week, sales of winter boots have risen 12 percent compared with last year (when the weather was warmer). Long-sleeved shirts also posted double-digit sales gains, according to Planalytics.
But the coast isn't clear yet.
Walsh and Bernhardt agreed that the biggest threat retailers face is another storm that weather models indicate could hit the Northeast next weekend. While they emphasized that it's too soon to make an accurate prediction for that weekend—the final Saturday and Sunday before Christmas—retailers wouldn't have enough time to rebound even online, as they couldn't guarantee by-Christmas delivery.
"That one will be bad news because there's no time to rubber band," Bernhardt said.
—By CNBC's Krystina Gustafson. Follow her on Twitter