Changes of air pressure in four weather systems

A, ① The weather system is a warm front. When the warm front crosses the border, the air pressure decreases, the temperature increases, and there is continuous precipitation, which does not meet the meaning of the question;

B, ② The weather system is an anticyclone, and the vertical airflow mainly sinks downwards, which does not conform to the meaning of the question;

C, ③ The weather system is a cold front. After the cold front passes, the temperature drops, the air pressure rises and the weather turns fine, which is correct;

D, ④ The weather system is a cyclone, and rainy weather often occurs during the cyclone transit, which does not meet the meaning of the question.

So choose: C.