(Amazon Photo)

Amazon’s Prime Day is back again for its fourth installment.

The retail giant is following up last year’s summer sales blowout, which it called the “biggest global shopping event in Amazon history” with an even longer Prime Day. This year, the window will be 36 hours, versus 30 last year, starting at 12 p.m. Pacific, July 16.

This will be the first Prime Day with Whole Foods Market under the Amazon umbrella, and the grocer will be front and center. Amazon promises an additional 10 percent off hundreds of sale items at Whole Foods and deeper discounts on some popular products. Amazon Prime Rewards Visa cardmembers will get 10 percent back on Whole Foods purchases, double the normal benefit, July 14 through 17.

Prime Day 2017 grew by more than 60 percent over the prior year, the company said. Amazon didn’t give specific numbers on deals, but last year it handicapped the number of sale items in the “hundreds of thousands,” while this year it is more than a million.

Prime Day has been a hit for Amazon. Taking a page from rival Alibaba, which hosts its Singles Day shopping event in China, Amazon in 2015 created the shopping holiday in mid-summer, one of the slowest times of the year. In just three years, Prime Day catapulted past Black Friday and Cyber Monday as Amazon’s busiest shopping day.

The shopping spectacular has also been a driver of Prime membership, which now stands at more than 100 million worldwide. Amazon said it signed up more new Prime members last year on Prime Day than any other single day in company history.

This year, employees will get a bit of a treat after the Prime Day dust settles. Amazon has canceled its long-running post holiday season celebration and summer picnic, choosing to replace it with a post-Prime Day concert, another sign of the importance of the summer buying bonanza.

Last year on Prime Day, the Echo Dot was the most popular purchase, not just among Amazon devices, but across all manufacturers and categories. This year, Amazon promises the biggest deals yet on Alexa-powered devices, and the tech giant has already knocked $100 off the price of Echo Show for Prime members to bring it down to $129.

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