It's beginning to feel a lot like Christmas.

A winter storm moving toward the Eastern third of the country is expected to douse the region with cold rain, sleet and snow in the two days before the Thanksgiving holiday.

While this probably will cause travel headaches for fliers and drivers, once they arrive at their destinations, the frigid temperatures and newly clear skies should put people in the mood to shop, according to retail experts.

Coupled with pent-up demand and cabin fever, the seasonable weather may give retailers a boost in traffic and sales over Thanksgiving weekend, when the National Retail Federation expects up to 140 million people to shop.

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"The best story in all of this, in my opinion, is that [the storm] clears out in time for a lot of the Thanksgiving shopping," said Scott Bernhardt, president of Planalytics, a consulting firm that analyzes weather's impact on consumer demand. "Everyone is in that holiday frame of mind—that's good news."

According to Planalytics data, major markets in the East are expected to be 10 to 25 degrees colder from Thursday through Sunday compared with the same period last year, and major markets in the Midwest, South Central U.S., Southwest and the Rockies region will also be much colder.

Temperatures likely won't be low enough to keep people inside, however, or even to prevent them from camping out for doorbuster deals, Bernhardt said.

Instead, experts said, the cold weather will help determine what people buy.

"If you're standing in a line to get into a store and you're freezing your butt off, you instinctively look for things that keep you warm," said Paul Walsh, chief meteorologist at The Weather Channel's WeatherFX.

Planalytics predicts that knitwear sales will rise nearly 30 percent over last year. Winter boots, as well as the hats, scarves and gloves category, should also see double-digit growth.

A Weather Channel online poll found that in the second week of November, 60 percent of respondents said they had worn heavy outwear the day before, compared with 25 percent the week before.

That will undoubtedly affect purchases, said Walsh, who said that in addition to current conditions, people decide what they will buy based on approaching weather patterns—known as the "forecast factor."

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What's more, he said, last holiday was unusually warm, so retailers have an easy comparison from that perspective.

Although the storm will prompt people to stay inside Tuesday and Wednesday, that shouldn't take much of a bite out of sales because they are not major shopping days, Bernhardt said. That's good for retailers such as Bon-Ton Stores, Dollar General and Christopher and Banks, as more than 25 percent of their stores are in the storm's crosshairs. Extending that metric to 20 percent, J.C. Penney, Sears, Kohl's, American Eagle, rue21 and Family Dollar will also be affected, but nowhere nearly as much as if it were to arrive on Thanksgiving or Black Friday, he said.

It's also a relief for retailers looking to get shoppers into stores. On Friday, analytics firm ShopperTrak revised its forecast for retail holiday traffic, saying it would be down more than 10 percent from last year, so any negative impacts from weather would be a blow. ShopperTrak founder Bill Martin said that the company's forecasts account for storms, as they typically play a heavy role in one region or another each year. Still, he said unless a widespread storm hits multiple states for many days, it usually won't move the national needle.

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But retailers aren't in the clear yet. Walsh said that while the storm is expected to have a positive impact on sales Thanksgiving weekend—particularly at department stores, specialty apparel stores and mass retailers—the shortened holiday calendar makes stores much more vulnerable to severe weather.

Because retailers have just four weekends instead of five, a major storm that hit on a weekend—especially the one right before Christmas—would have a much bigger impact.

"Retailers will be biting their nails as we go through, and hoping for seasonally cold and dry weather," he said. "All you need is one snow storm on a big weekend."

—By CNBC's Krystina Gustafson. Follow her on Twitter .