Elizabeth Weise

USATODAY

SEATTLE — Shoppers get ready to click: Amazon's second annual Prime Day sale will launch at midnight Seattle time on July 12.

The Seattle online retailer created the shopping holiday for its Prime customers last year as something like Christmas in July. It succeeded beyond Amazon's wildest dreams.

On 2015, Prime Day customers ordered 34.4 million items worldwide, breaking its Black Friday records. The shopping event launched on July 15 and marked the online retailer's 20th anniversary. And it's open only to Prime members.

At the time, Prime Day drew some negative comments with its wide and seemingly random offering of deals, causing critics to say merchants were using it to clear out unsold inventory.

Amazon sees it as more an eclectic, something-for-everyone sales event, said Amazon Prime vice president Greg Greeley.

"A certain deal that might seem weird to one customer might seem wonderful to another. That's part of the fun of Prime Day — discovering these unique items," he said.

This year's Prime Day will feature a run-up of five days of pre-Prime Day sales, each day offering a few deals to get customers primed (so to speak) for Prime Day.

Amazon says it will launch new deals as often as every five minutes over the 24 hours of the sale.

It will be available to new and existing members in the United States, the United Kingdom, Spain, Japan, Italy, Germany, France, Canada, Belgium, and Austria.

Competitors stepping up

Walmart president and CEO Fernando Madeira announced in a blog post Wednesday that the company will offer a free 30-day trial for ShippingPass, its competition with Prime. ShippingPass costs $49 a year and offers Walmart customers free, unlimited two-day shipping. Walmart customers who already have ShippingPass will get an extra month free.

Walmart said it will begin offering special deals July 1. In a dig at Amazon's one-day sale, Madeira noted Walmart's sales "typically last 90 days or longer while supplies last," and that its shipping program is about "half the price of similar programs out there."

Don't get excited about Amazon Prime Day yet

Prime important for Amazon

Prime members are important to Amazon's bottom line because they're highly lucrative. They spend on average about $1,100 per year, compared to about $600 per year for non-members, according to Consumer Intelligence Research Partners.

CEO Jeff Bezos said in the company's annual letter this year that he wants to make it indispensable.

"We want Prime to be such a good value, you’d be irresponsible not to be a member," Bezos wrote.

While Amazon doesn't release figures on Prime memberships, CIRP estimates that about one in five adult Americans had an Amazon Prime membership at the end of 2015, translating to about 54 million Prime members in the United States.