This year, we have had abnormal weather events worldwide and are expecting a highest temperature record since the emergence of human life on Earth. If such extreme climate events occur more frequently and become normal in the future, we will have an unprecedented climate. This study intends to answer to when we will have an unprecedentedly warm climate, focusing more on the regional characteristics of the timing of unprecedented climate. In this study, we used an in-situ observational data for annual-mean surface air temperature in Korea from 1973 to 2015 and estimated a timing of unprecedented climate using a linear regression method. Based on our results, an unprecedented climate in Korea is projected to come by 2043 in Cheongju at first and by 2289 in Mokpo at last. This 246-year gap in the timing indicates that a regional difference in timing of unprecedented climate is considerably large in Korea. In spite of a high sensitivity of the linear estimation to a data period and resolution, our findings on the large regional difference in timing of unprecedented climate can give an insight into making policies for climate change mitigation and adaptation, not only to the central government but also to provincial governments.l have an unprecedented climate. This study intends to answer to when we will have an unprecedentedly warm climate, focusing more on the regional characteristics of the timing of unprecedented climate. In this study, we used an in-situ observational data for annual-mean surface air temperature in Korea from 1973 to 2015 and estimated a timing of unprecedented climate using a linear regression method. Based on our results, an unprecedented climate in Korea is projected to come by 2043 in Cheongju at first and by 2289 in Mokpo at last. This 246-year gap in the timing indicates that a regional difference in timing of unprecedented climate is considerably large in Korea. In spite of a high sensitivity of the linear estimation to a data period and resolution, our findings on the large regional difference in timing of unprecedented climate can give an insight into making policies for climate change mitigation and adaptation, not only to the central government but also to provincial governments.