It's hard to deny that online sales are on a hot streak, consistently posting sales growth that outpaces bricks-and-mortar. Mobile sales, in particular, are increasingly contributing to that traction, accounting for 11 percent of total e-commerce dollars in the second quarter, according to ComScore.
Despite the rising share of desktop and mobile sales—which is expected to continue growing over the back-to-school period—their impact on the second-largest selling season of the year likely won't compare to the influence they have on the all-important holiday season.
"Shoppers continue to report shifting wallet share to the web because of the convenience of shopping online during key dates," Forrester Research said in a recent report. "Forrester's holiday estimates over the years have shown that a greater percentage of total sales happen online during the holiday season than any other time of the year."
Although Forrester analyst Sucharita Mulpuru said digital commerce is important year-round, there are a few factors that give it an extra boost over the holidays.
For one, shoppers are more pressed for time during the Thanksgiving to Christmas period, which means they have less time to spend at the store, said Andres Mendoza-Pena, a principal at A.T. Kearney. If they do make it out, their overall experience is typically more hectic, including more crowded stores, fewer parking spaces and longer checkout times—not to mention the cold weather.
"The Web picks up quite a bit of share during Q4 because consumers realize it's easier," Mulpuru said, adding online sales penetration tends to pick up 2 or 3 percentage points during the quarter.
But it's not just convenience that pushes consumers from standing in line to clicking online. One of the biggest reasons consumers opt to buy in stores stems from their preference to touch, feel and try on items. But because much of the spending over the holidays relates to buying gifts for others, this hands-on interaction isn't as important, Mendoza-Pena said.
Gifting's impact becomes even more important over the holidays because as more Americans receive smartphones, tablets and laptops, their penetration becomes even more prevalent, Mulpuru said.
"There are a lot of people that get phones and tablets during the [holidays] and then use their devices to do everything, including shop," she said.
The demographics tied to back-to-school shopping also put it at a natural disadvantage for mobile usage. According to a recent study by Kearney, millennials have the highest preference for using a combination of e-commerce and in-store shopping. But both Gen-Xers and teens, two groups with a higher influence on back-to-school spending, showed a higher preference for in-store shopping.
"Shopping malls are extremely attractive to [teens]," Mendoza-Pena said, adding that the group views them as a way to socialize.
Despite surveys from Accenture and the International Council of Shopping Centers showing the majority of back-to-school sales are expected to take place at the physical store, mobile's impact will continue to be felt—even when it isn't directly responsible for the sale.
According to a National Retail Federation study, mobile device owners plan to make more back-to-school purchases from their smartphones and tablets this year; likewise, more than one-third of smartphone owners will do research on their phones, up 2 percentage points from last year.
That means even if a purchase is completed in a store, technology can have a substantial impact. Consulting firm Deloitte predicted earlier this year that by the end of 2014, 50 percent of all bricks-and-mortar sales will be influenced by digital devices.
"I don't think that what you are reading is contradictory, even if at first sight it might seem to be," Mendoza-Pena said.
The retailers that will be successful, Mendoza-Pena said, are those that make it easy for consumers to shop both in a store and on digital devices. As such, a Forrester Research study found that mobile was retailers' most important initiative in 2014, though individual brands still vary greatly in their capabilities.
According to a recent study by mobile marketing company AppLovin, only 40 percent of the top 100 retailers, as defined by the National Retail Federation, allow users to make a purchase from within their app.
The impact of social networks also continues to lag, with only about 1 percent of visitors arriving at retail sites from Facebook, Pinterest or other sites, according to IBM research.
"These low numbers are unsurprising as social visitors are often eager to return to the social experience after a diversionary and unplanned 'curiosity click,'" the IBM report said.
Despite these headwinds, Forrester Research predicts desktop and mobile sales will reach a combined $294 billion in 2014.
"This is not a 100-meter race. This is a marathon," Mendoza-Pena said.
—By CNBC's Krystina Gustafson