Updated from 4:51 p.m. EDT

SAN FRANCISCO -- American Eagle Outfitters ( AEO) posted an unexpected drop in same-store sales for September, leading the teen-apparel retailer to cut its profit estimate for the third quarter.

American Eagle said its September same-store sales fell 2%, marking a sharp contrast to last year, when they soared 11% in the same period. Analysts had expected a 1.2% increase in same-store sales, or sales at stores open at least a year.

In light of the weaker-than-expected sales, American Eagle lowered its third-quarter earnings projection to 44 cents to 45 cents a share from its previous range of 47 cents to 48 cents. Analysts, on average, projected earnings of 48 cents a share, according to Thomson Financial.

The company blamed the sales drop on lower store traffic, particularly in regions that had warmer-than-average temperatures.

Same-store sales were particularly weak in the mid-Atlantic region, falling by a high-single-digit percentage, according to a company recording. Same-store sales dropped by a mid-single-digit percentage in the Midwest, Northeast and Southeast regions, but grew slightly in the Southwest.

American Eagle said its number of transactions per store fell slightly. The value of the transactions also slipped due to higher markdowns and a weak sales mix.

Although the company said it was pleased with its men's business, its women's business took a hit, with cool weather-related apparel and accessories selling poorly.

Christine Chen, an analyst for Needham & Co., says that while weather definitely played a role in American Eagle's results in September, the story goes further.

"Their women's product, while it looks good, it doesn't look differentiated enough," Chen says.

Chen adds that American Eagle has put itself in the difficult position of being a mid-level player while rivals Abercrombie & Fitch ( ANF) steals the higher-end shopper, while Aeropostale ( ARO) appeals to value-conscious shoppers.

The news isn't a good start for chain stores' sales reports, most of which will flood in Thursday morning. While weather is frequently blamed for sales shortfalls, analysts say it may have legitimately hurt results in September as warmer temperatures left fall clothes sitting on shelves.

Nonetheless, while American Eagle disappointed, smaller teen-clothing sellers managed to beat expectations.

Hot Topic ( HOTT) reported a 2.9% same-store sales drop for September, but that was slightly better than analysts' expectation for a 3% decline.

Zumiez ( ZUMZ), which sells sports-oriented gear, reported a 13.9% rise in same-store sales. That more than doubled Wall Street's expectation for a 6.6% rise.

Abercrombie and Aeropostale will report their September results Thursday. The teen sector overall is expected to show a 0.6% drop in same-store sales for the month.