Why is it suddenly so cold?

At present, it should be said that it is a cold current from Siberia and a warm current from the Pacific Ocean, so it rained several times not long ago. Because it is winter, the southern hemisphere has direct sunlight and Siberia has strong cold air. Geographically, it is called a cold front. After the cold front, the weather turned fine, the temperature dropped and the air pressure rose, so the weather you mentioned suddenly turned cold.