It is usual for the Han River to freeze up around December 3. In the 17th century, there were many occasions in which freezing happened in the river earlier than the usual time because of the early onset of bitter cold. Of total 15 cases of earlier freezing in the river, one occurred in September; four in October, and ten in early November. Freezing came as much as a month earlier in September or October than usual. The frequency of freezing was so high that it caused difficulties for people trying to make a living. On the other hand, it is usual for the Han River to thaw completely by the end of January. There were also several cases in which the river started to thaw or get frozen up later than usual. Five of those cases all happened in February because of late fury of bitter cold. Those cases of early freezing and late thawing indicate that there was extraordinary low temperature in the Seoul region those days, considering the meteorological conditions of freezing. They were caused by weather changes due to ongoing extraordinary low temperature rather than simple weather abnormality.
Frequent early freezing and late thawing ultimately led to the long freezing of the Han River, which in turn sent out shock waves to the people of Seoul that made a living according to the freezing and thawing date out of their long experiences. No boat, man, or horse would be able to cross the river when it was frozen or there was floating ice in it. In such a case, there was a risk that the nation’s administration would be paralyzed because official orders and documents would be postponed and officials on a business trip would be stuck somewhere. As foreign and domestic envoys were forced to postpone their traveL there was a risk of diplomatic issues and rising stay expenses. As the transportation of grains and commodities was suspended due to immobile boats, there was a risk of economic difficulties. Products in seasonal demand especially got hard blows. When the nation was faced with financial difficulties or in urgent need for relief due to frequent great famines, freezing would drive the situations to the worse possible scenarios. In case of freezing, fishing boats would not be able to leave the port, and fishermen would find it impossible to catch fish in the deep sea. It was natural for fishing people to have damage and for officials to get reprimanded for not making the deadline for the delivery of local products or not keeping their quality as promised.