In front of the Macy's flagship store in Manhattan's Herald Square, evidence of the retailer's Thanksgiving Day Parade was everywhere.
Rainbow confetti swirled on the sidewalk. Police barricades still lined the street.
But the shopping had already begun.
(Read more: Luxury cars expected to drive Black Friday sales)
"The sales are good," said Divya Quamara, 25, who stood in an Old Navy across the street from Macy's with her fiancé, Vinit Kelkar, 25. "And the stores are open."
Traditionally, the holiday shopping season kicks off on Black Friday, the day after Thanksgiving. But every year, more stores are opening on the holiday itself and keeping their doors open for longer, beginning in the predawn hours, before most turkeys even approach the oven.
In Annandale, Va., rock salt had been sprinkled on the parking lot in front of the Kmart that opened at 6 a.m. Though the temperature was just below freezing, a handful of shoppers were lured out of bed for discounted electronics or to browse in advance of Friday's sales. Wind had partly dislodged a plastic banner hanging above the entry.
Under a "Mas Navidad" sign near the customer service desk, Cindy Kennedy, 39, did not see why people would object to Thanksgiving store hours and people working the holiday. Northern Virginia is home to many immigrants, like her husband, who is from El Salvador, she said.
"I have a family, so I'll be spending it with my family, but other people don't, or it's not their holiday because they're not from here," Mrs. Kennedy said. "Not everybody celebrates Thanksgiving. It's not a world holiday."
Stores like J. C. Penney and Macy's were opening for the first time on Thanksgiving at 8 p.m., although others, like Toys "R" Us opened a few hours earlier. Old Navy was open until late afternoon, and then reopening in the evening, when some of its first customers will have a chance to enter a sweepstakes in which one person will win $1 million. And everything in the store will be 50 percent off.
(Read more: 5 ways to beat Black Friday deals)
This is a critical time of year for retailers, given that holiday season shopping generally accounts for about 20 percent of the retail industry's annual sales, according to the National Retail Federation. Last year, 139.4 million people went shopping through the Thanksgiving weekend, the federation said.
But with many Americans still struggling with stagnant wages, retail executives have warned of a lackluster holiday season. Anxiety about low traffic — in-store and online — coupled with tight budgets has spurred strenuous competition for the lowest possible price. Executives at Best Buy acknowledged that intensely competitive pricing on certain goods would most likely have a negative impact on its bottom line, even though its overall financial health has recently improved.
In a hurry to get to customers first, retailers introduced promotions not just a few hours early this year, but days and even weeks ahead. Walmart.com kicked off its holiday season on Nov. 1, for example.
According to the retail federation, 53.8 percent of shoppers surveyed during the first week of November said they had already started their holiday shopping.
"The early push is definitely noteworthy," said Traci Gregorski a vice president of marketing at Market Track, a retail promotion and pricing analysis firm. "There has been a lot of messaging around 'Don't wait until Black Friday.' "
And those who stayed home could easily browse the web. "Black Friday 2013 is here!" Amazon declared on Thursday. "Black Friday starts now online!" Walmart.com's homepage advertised. As of 6 p.m., online sales were up 10 percent over Thanksgiving Day last year, according to IBM Digital Analytics Benchmark.
(Read more: 8 ways to stick to your holiday budget)
Mobile traffic increased even more sharply, up more than 31 percent. Smartphones accounted for over 23 percent of all online traffic, IBM found.Friday's accompanying discounts, however, are still likely to draw out plenty of shoppers. According to a recent CBS News poll, Black Friday remains the most popular day to shop. A third of those surveyed said they planned to do some holiday shopping over Thanksgiving weekend
"I'm about to get myself a MacBook," Tony Portillo, 15, said, standing on the sidewalk in front of Best Buy in Falls Church, Va., where nine groups of shoppers formed an overnight campsite waiting for the store to open.
"You can't afford one!" came a voice from inside the tent, which was intended to sleep five people but on this below-freezing night was home to eight teenagers.
"Next time we need a bigger tent," said Mr. Portillo, who planned to wait until 6 p.m. for Best Buy to open.
"We didn't sleep at all," said Alex Ramos, 14. "It's kind of fun."
Some retail analysts and industry watchers have said that the extension of shopping hours further into Thanksgiving, as opposed to the overnight openings in recent years, means more teenagers are taking part in Black Friday weekend. Their curfews now permitted them to take part in sales, and perhaps, some allowed, it provided an excuse to escape an entire day trapped in the house with their parents.
In addition to new shoppers, there have also been protests, as a holiday devoted to family and carbohydrates becomes increasingly about cheap televisions and half-price sweaters.
(Read more: Shoppers beware—the 12 scams of Christmas)
But while labor advocates and some workers bemoan the expanded shopping hours (and three-fourths of Americans in that same CBS News poll believe stores should be closed on Thanksgiving), plenty of shoppers streamed into stores around the country.
At American Eagle Outfitters on 7th Avenue in Manhattan, the entire store's inventory was 50 percent off on Thursday, and by 4 p.m., it was packed.