This study aims to investigate the effects of climatic variability on the citrus yield in Jeju-do. This study analyzed the relationship between the citrus yield and climate elements(temperature, rainfall, sunshine duration etc) at each growing season. Temperature shows a positive relationship with the period of flower bud for the yield of citrus. The rainy days of bud bursting period have a negative relation in Seogwipo area. The sunshine duration of the 1st physiological fruit drop period was positively related to citrus yield in Jeju and Seogwipo area. The maximum temperature of the 2nd physiological fruit drop period and the fruit enlargement period were negatively related to the citrus yield. In Jeju and Seogwipo area, about 60% of the variation of citrus yield is explained by the variation of climatic factors. The sunshine duration of the 1st physiological fruit drop period and fruit enlargement period were selected to the yield estimation in Jeju. In Seogwipo, the number of rainy days and the sunshine duration of the 1st physiological fruit drop period were selected.