Other than a later Easter (it fell in March last year) sales were boosted by un-seasonally warm weather last month. ICSC's research team estimates that sales were up 1% as a result of the warmth.

Apparel had the biggest increase from March's showing. Clothing stores were up 5.9% in April, after falling 3.6% the previous month. American Eagle Outfitters led the way, soaring 19%, followed by Abercrombie & Fitch and Cato, which were both increased by 17%.

Discounters, rising 7.4%, were also up significantly from March, when they inched up 1%. Target soared 10.4%, followed by Wal-Mart, shooting up 7.3%. TJX Cos. were at the low end of the sector, slightly up 1%.

Department stores, at 5.3%, were mixed. While Kohl's was up 13.4% and Dillard's rose 10%, Federated Department stores dropped 0.8%.

Wholesale clubs were one area of the industry that had lower results in April--falling 0.3%, to a 5.3% rise--than in March. Costco was the leading chain, up 7%, contrasted by BJ's Wholesale, which increased 1%.

ICSC's research team expects a 3% to 3.5% year-over-year improvement in May. The sharp rise is energy prices are expected to impact consumer spending.