The weather in Shenyang

A, the wind speed in the chart on the 29th changed little, and there was no precipitation, so A was wrong;

B, 3 1 has the largest precipitation, the largest wind speed and the largest temperature change, which accords with the weather characteristics of cold front crossing, so B is correct;

There is no precipitation on C, 1, and the temperature has hardly changed. It is the weather after the cold front crosses the border, so C is wrong;

There was no precipitation on days D and 3, and the temperature hardly changed. It's the weather after the cold front crosses the border, so d is wrong;

Therefore, choose: B.