The electricity supply commonly used in Korea is the 200-volt 60Hz system. Because most newly built hotels and houses have the 220-volt wiring installed, you are advised to check your electronic equipment beforehand.
The annual average temperature in JEJU Island is relatively low, compared with other places at the same latitude, due to cold winter seasons, an influence of continental climates, and summers that do not become too hot due to cool oceanic currents. The average annual temperatures of JEJU are reported to be 15.5 oC and 21.5 oC of June's average temperatures.
The Korean local currency is the Won. Major foreign currencies that can be exchanged at banks, hotels, and the airport include the US Dollar, Japanese Yen, Euro, and UK Sterling. Most hotels, restaurants, and shops accept major international credit cards including Visa, American Express, Diners Club, Master Card, and JBC. Foreign-issued ATM cards may have limited use.