The weather in Beijing is really cold. It's a cold current from Siberia. What does this conversation mean?

During the Sino-Soviet War, the foreign minister of the former Soviet Union flew to Beijing and Premier Zhou Enlai met him. Because the relationship between the two countries is not good, there is no red carpet and no welcome crowd. The foreign minister saw this scene as soon as he got off the plane. Then he shook hands with Premier Zhou and said, "It's so cold in winter in Beijing." Premier Zhou said: "This is a cold current from Siberia." Pun.

Note: Siberia is a vast area of North Asia in Russia.

I hope these answers can help you