Safe is a relative term. This side of private options (and even then) there are no safe bike racks. That said, the 16th/Locust Patco stop is fully covered and has decent racks. Bikes have definitely been stolen from there. That said, one time I even had trouble with my own lock and a cop came down and asked me about it until I showed him the key was just stuck.

YMMV, but it is def dry.