Wall Street's worries about a double-dip recession overshadowed the good sales figures posted by retailers for July, including strong numbers from Seattle-based Nordstrom and Costco Wholesale.

Nordstrom said Thursday that sales at stores open more than a year, also called same-store sales, increased 6.6 percent in July, boosted by the popularity of the Anniversary Sale that ended Sunday. Analysts had predicted only a 5.8 percent rise in same-store sales.

The department store chain, which operates 213 stores in 29 states, said that its Southern and Northwest locations were among its top performers last month, while California continued to underperform. Top-selling categories were women's shoes, dresses and cosmetics.

Nordstrom was among the 65 percent of retailers that beat analysts' expectations for the month, according to Thomson Reuters. Yet investors hammered its stock, sending shares down $4.60, or 9.6 percent, to $43.15.

Costco was among the retail industry's best performers in July, posting same-store sales of 10 percent. The average amount shoppers spent there rose 8.5 percent.

Still, its stock fell 57 cents, or 0.7 percent, to $76.51 on Thursday.

In the U.S., Costco's same-store sales climbed 6 percent despite stores being closed on the July 4 holiday. The warehouse chain figures it lose 3.5 percent because of the lost day; oddly, it included the July 4 closures in its June figures last year.

Its strongest U.S. regions in July were the Midwest, Texas and the Southeast.

California was not cited, which was "disappointing" to ThinkEquity analyst Edward Weller.

He was counting on strong sales particularly in Costco's southern California region, which the company lumps with figures from Arizona and Nevada, for it to reach his fiscal year earnings estimate of $4 to $4.05 a share.

"Southern California accounts for something approaching one third of the U.S. business," he wrote in a note to investors.

Internationally, Costco's same-stores sales rose a whopping 22 percent.

Results from two smaller Seattle-area retailers suggested they are struggling.

On Thursday, Internet jeweler Blue Nile posted a lower-than-expected profit for the second quarter, citing rising wholesale diamond prices and a weakening U.S. economy.

Blue Nile's quarterly profit of $2.8 million, or 19 cents a share, was virtually the same as a year ago. Its sales for the three months ended July 3 rose 5.1 percent to $80.5 million.

Analysts had been expecting a per-share profit of 22 cents and sales of $84.1 million.

Shares of Blue Nile fell more than a dollar to $35.48 in after-hours trading Thursday. The stock had closed down $3.28, or 8.2 percent, at $36.59 before the earnings report.

Also, Blue Nile announced that co-founder Mark Vadon will remain chairman of the board but no longer will serve as executive chairman. Vadon stepped down as the company's CEO and became executive chairman in February 2008.

Shares of Everett-based Zumiez plunged $5.33, or 20 percent, to $21.77 on Thursday after posting a same-store sales increase late Wednesday that fell short of expectations.

Zumiez said same-store sales rose 4.9 percent in July, well below the 7.5 percent analysts predicted. A year ago, the youth-oriented apparel chain reported a 9.4 percent increase in same-store sales.

Despite a flow of bad economic news that kept consumer confidence shaky, a number of retailers reported July sales on Thursday that beat Wall Street estimates, including discounter Target, department store Macy's, and luxury chain Saks. The International Council of Shopping Centers' preliminary tally of retailers' same store sales — a key indicator of a merchant's health — was up 4.6 percent, a slower pace than June's 6.9 percent gain but in line with forecasts.

While the numbers signal a strong start to the back-to-school shopping period, which runs roughly between mid-July through September, there are concerns that shoppers will soon return to their habits of the Great Recession by focusing on necessities and waiting for sales. That could be a big problem for retailers, which are raising prices in order to offset with rising fuel, labor and other production costs.

"Early going, July looks like it's shaping up to be a solid month despite all the economic headwinds," said Ken Perkins, president of RetailMetrics, a research firm. "But the concern is whether shoppers will buy back-to-school items at full price."

The concern stems from the fact that while the recession officially ended in June 2009, many shoppers, particularly in the low-to-middle income bracket, feel like it never ended. After all, the economic picture for most has not improved.

For many, wage gains haven't kept pace with higher household costs for food and gas, which is $1 more per gallon than a year ago. Home values remain depressed, and companies are not hiring. Adding to that, this fall, shoppers will face higher price tags as retailers try to offset higher labor costs in China and prices of raw materials.

In this environment, retailers that cater to higher-income shoppers have fared the best. The biggest standouts have been luxury retailers like Saks, which had a 15.6 percent increase for the month. That was much higher than the 8.5 percent forecast

Even retailers who cater to low- and medium-income shoppers, who have been most hurt by the economic downturn, posted sales gains for July.

Target, which has been beefing up its grocery business, said revenue at stores opened at least a year rose 4.1 percent as shoppers picked up more groceries and health and beauty products. Target said consumers spent more per transaction and it expects the key revenue measure to rise in the low- to mid-single digits in August. The company said back-to-school sales are off to "a solid start."

Many department stores also had respectable results as they drew shoppers in with exclusive merchandise and sales on select items. J.C. Penney Co.'s 3.3 percent beat the 2.3 percent estimate from Wall Street. And Macy's Inc. posted a 5 percent gain, which exceeded the 4.1 percent forecast.

Macy's, which also runs Bloomingdale's stores, benefited from growing online sales. CEO Terry Lundgren also said that "fresh, interesting and distinctive merchandise," a "re-energized" culture, and better employee sales skills, also helped.

The hope among retailers is that the July sales momentum will continue into August, with shoppers picking up a few fall items at full price while buying some summer bargains, too. But surveys from the National Retail Federation, Deloitte L.L.P. and other groups show that customers plan to buy only what the family needs, focus on fat discounts and reuse last year's items.

"It's going to be tough for retailers to succeed because of the economic uncertainty," said Stifel Nicolaus analyst Richard Jaffe.

The back-to-school season is important for retailers because it accounts for 16.1 percent of annual retailers' revenues, according to the International Council of Shopping Centers. It's also an opportunity for retailers to gain insight into consumers' shopping habits heading into the biggest shopping season of the year, which starts on the day after Thanksgiving.

Retailers will get a better sense of how shoppers are spending during the back-to-school shopping season in August. So far, analysts and retail trade groups are sticking to their forecasts for the season, ranging from unchanged to 3 percent compared with a year ago. The National Retail Federation expects families to spend $603.63 on back-to-school items, from clothing to supplies, down slightly from last year's $606.40.

But not every retailer posted encouraging results during the beginning of the back-to-school season. Gap said it had a 5 percent drop in revenue at stores opened at least a year in July, worse than the 0.7 percent decline that analysts had expected. Its namesake division, Old Navy and Banana Republic as well as its overseas business, all posted drops. Still, the retailer offered a profit outlook that was above Wall Street estimates because of improvements in inventory.

Department-store chain Kohl's Corp. also posted disappointing results, with a 4.6 percent drop. That was well below the 3.4 percent gain that Wall Street analysts had expected. And teen retailer Aeropostale Inc. had a 14 percent drop in revenue at stores opened at least a year.

"We are very disappointed with our second-quarter financial results that were clearly unacceptable," said Thomas P. Johnson, chief executive officer at Aeropostale in a statement.

The Associated Press contributed to this report.

Melissa Allison: 206-464-3312 or mallison@seattletimes.com