˜e onset, retreat, and precipitation of the Korean summer rainy season (Changma) signiÿcantly a˛ect human health and daily lives as well as domestic industry and economy. To increase revenue during Changma period, retail industry has tried to develop various weather marketing strategies on a regional basis. This study investigated the impact of Changma on the retail sales in Jeju. During Changma in Jeju in 2014, the temperature has dropped by 2.3°C, from 26.2°C to 23.9°C while the precipitation has significantly increased from 115.3mm to 441.5mm compared to last year. Due to these weather characteristics of Changma, large retailers in Seogwipo city have seen a high increase in sales of umbrellas, raincoats, and rain boots by 250-400 percent, but a decrease in sales of air conditioners by 15 percent. This results from more frequent rainfall and cool weather compared to the previous year. However, opposite results were found regarding traditional markets in Jeju. Depending on industrial structures in each region, the identical weather phenomenon have different impacts on the number of visitors to the markets. In other words, the impact of Changma on local retail sales is in˝uenced by multiple local factors including demographic composition and industrial structure in the regional economy.