By Dhanya Skariachan

NEW YORK (Reuters) - Deep discounts and the warmest July weather in decades should help retail chains report a rise in monthly sales, with many expecting warehouse clubs and high-end chains to lead the way.

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

Chains ranging from Target Corp <TGT.N> to Saks Inc <SKS.N> will report closely watched sales at stores open at least a year on Thursday.

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.

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

An early batch of results highlighted mixed fortunes.

Teen apparel chain Zumiez Inc <ZUMZ.O> 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 and hard goods.

Rival Hot Topic Inc <HOTT.O> blew past estimates with a 7.3 percent rise in same-store sales, prompting it to forecast a narrower-than-expected loss in the quarter.

Top U.S. drug store chain Walgreen Co <WAG.N> reported a 2.7 percent rise in July same store sales, beating the analyst estimate for a 2.5 percent increase as strong sales of candy and other front-end merchandise offset weak pharmacy sales.

MARGIN-SAPPING DISCOUNTS?

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.

Analysts expect warehouse club operators such as Costco Wholesale Corp <COST.O> and BJ's Wholesale Club Inc <BJ.N> to post some of the largest sales gains in July.

Many also expect healthy sales gains at dollar stores, off-price chains TJX Cos <TJX.N> and Ross Stores Inc <ROST.O> and luxury chains Saks Inc <SKS.N> and Nordstrom Inc <JWN.N>.

One underperformer of the month could be clothing retailer Gap Inc <GPS.N>. Same-store sales at the parent of the Gap, Old Navy and Banana Republic chains are expected to fall 0.7 percent, according to Thomson Reuters data.

(Reporting by Dhanya Skariachan in New York, Eunju Lie in Chicago, Arpita Mukherjee and Meenakshi Iyer in Bangalore; Editing by Bernard Orr)