PHILADELPHIA — It's beginning to look a lot like Christmas — and it's only October.

Santa isn't here yet, but retailers already are stocking shelves with Christmas merchandise, in some cases setting up Christmas trees and holiday lighting way before Thanksgiving and even pre-empting Halloween.

Wal-Mart Stores Inc., Target Corp. and J.C. Penney Co. are some retailers hoping to get consumers into a Christmas shopping frame of mind two months early. Sears Holdings Corp.'s Sears and Kmart stores kick off the Yuletide mood in late October or early November. Costco Wholesale Corp. said it's always put out Christmas ornaments, gift wrap, cards and artificial trees as early as September.

"Although our busiest Christmas sales weeks will occur in November and December, we have been placing a selective sampling of our Christmas items into stores early in the season for several years," said Tara Raddohl, a spokeswoman for Bentonville, Ark.-based Wal-Mart.

MORE JOINING IN

The trend began about three years ago, but more retailers are joining in, said Britt Beemer, chairman of America's Research Group, a consumer behavior marketing firm in Charleston, S.C.

It's a phenomenon called "Christmas creep," according to the Wharton School at the University of Pennsylvania in Philadelphia. Hoping to catch early shoppers, retailers are extending their all-important holiday shopping season, which accounts for 25 percent to 40 percent of the year's sales.

"The creep has been going on," said William Cody, managing director of the Baker Retailing Initiative at the Wharton School. "Every year, retailers hope that coming out early is going to reduce the amount of promotions. They'd rather people buy at full price."

Shoppers who spot a Christmas item they fancy might not want to wait for the product to go on sale a month later for fear it would be sold out. So they'll buy it at full price, Beemer said.

But it's still not clear whether the strategy adds significantly to profits, Cody said. Retailers haven't reported any big jumps in sales or profits pegged to an extended Christmas shopping season.

At The Parks at Arlington mall in Arlington, Texas, several shops already have Christmas trees in window displays, said Cindy Thompson, the shopping center's marketing manager.

"It looks like Christmas is starting early," she said.

Part of the stores' strategy is to capture more sales by letting people shop early, she said. That's why, for the first time this year, The Parks and five other malls owned by General Growth Properties in the area will open at 6 a.m. the day after Thanksgiving, the traditional kickoff of the holiday shopping season known as Black Friday. Other opening times will vary, but the half-dozen malls will close at 10 p.m. daily from Black Friday until Dec. 23.

NOT TOO EARLY, THOUGH

Some retailers, such as Costco, have always set out their Christmas goods ahead of others.

"We put it out very early," said Gary Ojendyk, Costco's general merchandise manager. "There's a lot of small-business people that buy products from us and resell the products."

But retailers have to be careful not to push Christmas in October too aggressively because they don't want to risk alienating shoppers.

"It's too early. I think they should start after Thanksgiving," said Kim Nelson, a shopper at Macy's in downtown Philadelphia. "They just want to rush everything."

While the 37-year-old resident of Glen Mills, Pa., doesn't want to see Christmas decor at malls before Thanksgiving, she admits that she shops early for the holidays.

She's not alone. The National Retail Federation, an industry trade group in Washington, D.C., said 40 percent of consumers plan to start their holiday shopping before Halloween this year.

"The demand for holiday merchandise is there," said Kathy Grannis, the group's spokeswoman.

As Christmas comes ever earlier, it's given Thanksgiving merchandise the boot.

"Thanksgiving items are really something of the past — the pilgrims, the turkeys," Beemer said.

HALLOWEEN BOON

What hasn't been hurt is Halloween. Halloween is becoming a bigger holiday as more adults join in. What's particularly popular are decorative inflatables such as pumpkins, Cody said.

According to a survey by the retail trade group, nearly two-thirds of consumers plan to hold Halloween celebrations this year, up from 52 percent last year. Consumers said they plan to spend 22 percent more on average this year: $59 per person.

Among 18- to 24-year-olds, 85 percent plan to celebrate Halloween, up from 67 percent in 2005.

As such, retailers have no qualms about putting Christmas goods out early, alongside Halloween items. But they probably won't push Christmas as early as summer.

"Are we going to see Christmas in July? No," Grannis said. "The back-to-school season and every other holiday is important for them, too."