"We believe cooler weather during the month combined with higher interest rates and gasoline prices could translate into slower sales for retailers, especially in seasonal merchandise," says Christine Augustine, a Bear Stearns analyst who follows department stores, in a note to investors. She also points out that gas prices are 4% higher than the same period last year.

Some of the companies that Mitchell Kaiser, a Piper Jaffray analyst outlined in a report, face the difficult comparisons to last year. Costco, which he is forecasting at 3% year-over-year same-store sales increase during last month, is up against a 16% jump in May 2004. Big Lots, predicted to have a 2% increase, was up 7.4% last year.

But Lehman Brothers analyst Jeff Black expects at least two of the teen apparel chains he covers to do well. He is forecasting a 16% jump for Abercrombie & Fitch, and a 15% hike for American Eagle Outfitters, compared to last year's gains of 1% and 10.6%, respectively.