I have a question about proper electrical box for damp location. If a light is mounted on 'inside' ceiling of a covered porch, and the wire going to the light is in proper conduit and rated for damp/wet locations (THWN).

Is a weatherproof box required if you were to mount a light to one of the rafters of a porch like this?

Example picture:

Can either a steel or weatherproof box be used?