Deep discounts and the warmest July weather in decades brought shoppers to malls, helping many retail chains report healthy monthly sales increases at established stores.

July figures provide an early read on consumer demand in the U.S. economy at the start of the back-to-school season, the second-biggest selling period of the year after Christmas.

Warehouse club Costco and teen apparel chain Hot Topic posted some of the biggest gains so far.

Costco Wholesale Corp reported a 10 percent rise in total July sales at stores open at least a year, beating the analysts' average estimate of an 8.6 percent increase.

Warehouse clubs, which charge an annual fee to shop in their stores, have won customers seeking low prices on necessities such as groceries or toiletries. Costco has also gained from higher gasoline prices.

"They are starting to really take advantage of really a gold mine they have been sitting on for years, which is their ability to target their individual members with specific deals and discounts through mobile devices," said Alison Paul, leader of advisory firm Deloitte's U.S. retail practice.

Limited Brands reported a 6 percent rise in same-store sales, beating the analysts' average estimate of a 4.2 percent increase. The strong performance prompted the parent of the Victoria's Secret and Bath & Body Works chains to boost its earnings estimate for the just-ended fiscal second quarter.

Teen apparel chains Hot Topic Inc and Wet Seal blew past estimates. Hot Topic reported a 7.3 percent rise in same-store sales, well above the analysts' forecast of a 0.5 percent increase, prompting it to forecast a smaller quarterly loss than Wall Street was expecting.

Chains ranging from discounter Target Corp to high-end department store chain Saks Inc will also report closely watched same-store sales on Thursday.

Overall, analysts are expecting same-store sales to rise 4.3 percent in July, compared with a year-ago increase of 2.8 percent, according to Thomson Reuters data. 

The United States had its warmest July in 50 years, according to Planalytics, a company that tracks weather for businesses.

"Recent hot weather has driven consumers to the malls, aiding in the clearance of spring and summer merchandise," Barclays analyst Robert Drbul said.

Top U.S. drugstore chain Walgreen Co reported a 2.7 percent rise, just ahead of the analysts' average estimate of 2.5 percent as strong sales of candy and other front-end merchandise offset weak pharmacy sales.

Teen apparel chain Zumiez Inc reported a 4.9 percent rise in same-store sales, missing the analysts' estimate of a 7.5 percent increase. The company blamed the weakness on lackluster sales of accessories.

Investors will want to know if retailers had to offer deeper-than-usual discounts to win shoppers.

U.S. consumer sentiment fell in July to its lowest point in more than two years as anxieties over stagnant wages and unemployment deepened, a survey showed.

"My mom is paying the bills, and they're telling me that they need to cut back on me spending all this money on me buying clothes," said Ed Rush, 15, who was shopping at a Target store in Chicago.