Hype around Amazon’s biggest event ever — Prime Day — is at full tilt, and it’s even spilling over into competing retailers.

After creating the summer shopping “holiday” last year with discounts and deals for Prime members, Amazon is offering more deals and more merchandise in an effort to combat the sell-outs of last year. Analysts from MKM anticipate that Amazon might even double last year’s sales volume of as much as $400 million.

By way of comparison, Alibaba’s Singles’ Day shopping event on Nov. 11, which it created in 2009, last year did a record $14.3 billion in sales.

This is the second year Amazon will offer “more than 100,000” deals only for Prime members. It started the holiday in honor of its 20th anniversary to increase summer sales and lure in more Prime members. Prime members pay $99 a year for perks such as free two-day shipping on many items and streaming of movies and TV episodes.

Last year, Prime Day was the single biggest day for sales for Amazon. J.P. Morgan, in a research note, said that it believes that Prime Day “pulls forward demand during an otherwise quiet retail period and serves as a critical peak-day test for Amazon’s fulfillment and distribution operations ahead of the holiday season.”

Amazon did not share any fashion-related deals in advance, or information on fashion-specific insights from last year. In 2016, there were some “healthy discounts” on clothing, shoes and jewelry as well as cell phones and cell-phone accessories, said Katherine Wilson, director of marketing insights at Clavis Insight.

According to a survey by Cowen & Co. analyst John Blackledge, the company’s Prime Now service, which delivers more than 10,000 goods within two hours, is finding a ready customer base in fashion. The Cowen survey suggested that 25 percent of U.S. Amazon Prime subscribers purchased something on Prime Now in January and 41 percent of the Prime Now customers bought an item in the apparel, shoes or accessories area. Research firm L2 predicts that in 2016, Amazon is set to overtake Macy’s as the largest apparel retailer in the U.S.

There are early indications that, just as Hallmark’s Valentine’s Day and Alibaba’s Singles’ Day have done, Prime Day stands to bleed out beyond just Amazon. Last year, according to performance marketing service HookLogic, retail site traffic spiked outside of Amazon.com and conversions were 16 percent higher.

HookLogic found that traffic of mass merchant U.S. e-commerce sites across the Retail Search Exchange network, which includes retailers such as Target, Best Buy, Macy’s and Wal-Mart, was 1.8 times higher on Prime Day than it was compared to the week before. The top traffic winners, by category, were apparel and accessories, electronics, sporting goods, home and garden and furniture.

J.P. Morgan also made note of response from competitors, as retailers offered online sales of their own: Wal-Mart offered thousands of deals and reduced its free shipping minimum order to $35 from $50, it noted, while Macy’s hosted a Surprise Specials Day with online discounts and free shipping on all orders for the first time.

J.P. Morgan said that it expected that many retailers would introduce sales this year, such as Wal-Mart offering a free 30-day trial of ShippingPass, with online sales having already started on July 1. There also are early deals on Amazon available, including promotions through Amazon’s Alexa that allow for voice ordering of products such as a drone or Cuisinart.

The full spate of Prime Day deals will become available on Amazon starting at 3 a.m. on Tuesday.