According to the "Nanchang Evening News" report on April 28, 2009, the weather forecast temperatures in Nanchang during the May Day holiday are as follows: Time April 29 April 30

The temperature difference on April 29 is: 22-18=4℃.

The temperature difference on April 30 is: 24-18=6℃.

The temperature difference on May 1st is: 27-19=8℃.

The temperature difference on May 2 is: 22-18=4℃.

The temperature difference on May 3 is: 24-19=5℃.

So choose C.