Sales at convenience stores fell 2.6 percent in September from a year earlier, marking the third straight month of decline, the Japan Franchise Association said Friday.
The percentage change, adjusted for variations in the number of stores, is based on stores that have been open for at least one year and excludes those that opened or closed during the period.
The number of customers also dropped 0.5 percent for the second straight month due partly to lower-than-usual temperatures in September and typhoons, it said.
Average spending per customer fell 1.2 percent, with declines likely to continue, it said.
Sales of summer items like beverages and ice cream were sluggish, while warm buns, tea and canned coffee sold well.
Sales at all stores, including new ones, came to 555.62 billion yen in the month, up 1.8 percent.
The figures cover outlets run by 14 major convenience store operators.