School shopping shifts earlier thanks to Amazon Prime Day

  • Amazon's Prime Day is pushing the back-to-school season earlier in the year.
  • Other retailers are "drafting" off the online merchant's success.
Jamie Grill | Getty Images

The school year starts early these days, and you have Amazon to thank for that.

Retail shoppers are taking advantage of the online giant's Prime Day to get a jump on back-to-school shopping for the fall semester. Amazon's annual event offers subscription members various deals over a 30-hour period in July.

Fresh data provided to CNBC show how shopping for back to school is starting earlier in in the year. Online-only shopping for back-to-school peaks the week of Prime Day, long before many brick-and-mortar stores have rolled out their displays, according to Cardlytics, a firm that tracks purchasing data.

"Retailers should start marketing their online channels at the beginning of the summer, to capture the early online spend," said Dani Cushion, chief marketing officer at Cardlytics, "and their in-store channels mid-summer through the start of the school year."

The summer is normally a dry spell in the retail calendar, which is one reason for the positioning of the promotions. The back-to-school shopping season is second in importance only to the holidays for retailers' bottom lines.

Amazon's Prime Day began in 2015 as an anniversary of the company's first 20 years. Customers were initially disappointed by the sales, but sales volume still exceeded Black Friday sales from 2014. Other retailers took notice and many followed suit, offering their own deals to coincide with Prime Day in 2016.

On Monday, eBay sent an email to customers announcing "It's Prime Time!" Macy's website advertised "Black Friday in July" with a timer ticking down to midnight. Home Depot executives told analysts in a recent earnings call that the company was having luck "drafting off Prime Day."

"Rivaling holiday spend, the back-to-school shopping season is a critical time for marketers to boost total annual sales," Cushion said. "While we're seeing growth in online spend, brick-and-mortar spend is still significant."

Back-to-school retail spending grew by 5 percent in 2016 over 2015, driven largely by online-only sales, according to Cardlytics' data. Still, dollars spent in brick-and-mortar stores made up three-quarters of the total in 2016.