Amazon is giving new meaning to the phrase “Christmas in July.”

The online giant’s third annual Prime Day event may not surpass Black Friday sales, but it is poised to be the largest Prime Day to date, according to a survey Market Track LLC, a provider of subscription-based advertising, brand and pricing intelligence solutions. Fifty-eight percent of consumers plan to shop Prime Day sales, up from 34% last year. The growth comes, in part, because of Amazon’s increased participation in its Prime program and momentum from the publicity surrounding previous Prime Day discounts.

One reason that Prime Day may not exceed Black Friday sales volume could be that prices for key shopping categories were consistently lower for holiday shopping events like Black Friday and Cyber Monday than on Prime Day. Across the categories and…