The unusually long and cool rainy season has dampened demand for apparel, furniture and other goods, with some retailers already reporting steep drops in merchandise sales.

Shimamura Co., a chain of affordable clothing shops, reported last week that same-store sales through July 20 fell 18 percent from a year earlier. Many of Shimamura's customers reach the company's 1,433 locations in Japan via bicycle rather than car, so rainy days tend to have an outsized impact on revenue, a spokeswoman said.

So far, Tokyo has seen only about 44 daylight hours in July, among the least since the Meteorological Agency began keeping records in 1890. There was one less Sunday this year compared with July 2018, and rain and overcast skies also appear to be keeping people at home, especially on weekends. Given that Japan's retailers, especially Uniqlo operator Fast Retailing Co., are sensitive to seasonal weather trends, they will probably report weaker monthly sales in the coming week, according to Michael Allen, an analyst at Jefferies.