We are going to the Dragon's backbone in April and will be doing a walk of 4 to 5 hours.

There are several days in the early Apr. or mid Apr. without rain. Even if it rains, it wouldn’t rains all the time.
The temp in early Apr. is 55-68F. So you may need to wear long sleeved shirt and a thin coat as well as sports shoes if walking. In addition, remember to take umbrella.