As your inbox no doubt reminded you this morning—perhaps incessantly—this is the last weekend to shop before Christmas.
Retailers are making their last-ditch pitches to get people into their stores, sending emails that broadcast aggressive promotions, including offers that in many cases match or exceed those on Black Friday.
(Read more: Time to blame gmail for challenging holiday sales?)
"This is really the make-or-break weekend, because it has been a very soft retail Christmas season," said Britt Beemer, chairman of America's Research Group. "I think you're going to see 50 percent off more aggressively promoted this weekend."
According to Experian Marketing Services, as of Dec. 14 email volume from retailers this holiday season was up 7.4 percent from last year. Particularly popular subject lines have been daily deals and shipping deadlines, which reflect shoppers' focus on price and convenience.
Such customized subject lines helped improve unique open rates for these mailings, a metric that is important for retailers in winning shoppers online, Experian said.
Blair Lyon, vice president of marketing at Monetate, said, "Marketers that want to outperform the market must focus on delivering a winning customer experience. ... That means being more relevant, not simply sending more email."
The flood of targeted emails is just the latest move in a competitive holiday environment that has already seen a dose of heavy discounting. Anemic foot traffic and a shorter holiday calendar have led to retailers' trying to outdo one another every step—from keeping stores open for 24 hours to slashing prices.
But a lot is at stake this weekend in particular.
According to analytics firm ShopperTrak, store traffic fell nearly 20 percent last week, hurt by the winter storm that covered the Northeast and Midwest with snow and ice. The firm predicts that this Friday, Saturday and Sunday will rank among the top four busiest days of the holiday season, making it critical for retailers to capture sales.
(Read more: Storms walloped retailers, shoppers stayed home)
ShopperTrak founder Bill Martin said one positive is that stores will have a stronger advantage when people walk in, because many have already done their window-shopping online. That results in higher conversion rates.
"There's a high-value asset that's now walking into the store," he said.
Despite a severely short window, some retailers are still pushing free shipping offers to attract procrastinators. Saks, Neiman Marcus and L Brands' Victoria's Secret are offering free express shipping to online shoppers, while Amazon is offering a free 30-day trial of its Prime service. Customers who sign up for the trial can receive free two-day shipping on orders placed as late as midnight Sunday.
(Read more: Web sales on a billion-dollar hot streak)
Beemer at America's Research Group said all the 11th-hour promotions reflect customer habits. While Black Friday deals catch the early birds, sales in the last few days before Christmas cater to procrastinators. And with one less weekend between Thanksgiving and Christmas this year, many shoppers are under the gun.
According to the National Retail Federation, as of Dec. 9, 32 million people had not even started their holiday shopping.
Because of the weak start, Beemer said, smart retailers would be offering 60 percent to 70 percent discounts to get shoppers in the door on such a crucial weekend. But that probably won't happen, he added.
"They're going to gamble," Beemer said. "They're going to try to keep margins intact as best they can."
The same likely will not hold true after Christmas, though, as they try to boost their December numbers with even more drastic discounts, he said.
Experian data indicate that emails offering discounts of half off or more are likely to peak during after-Christmas sales.
And Beemer said that consumers will see "50 percent off, plus an extra 10 percent off 'this week only.' "
—By CNBC's Krystina Gustafson. Follow her on Twitter .