Probably not. There's DC on the terminals, which means corrosion is an issue. You need to either make the connection in such a way that it can dry out readily if it does get wet (Tamiya connector style) or waterproof it so it doesn't get wet in the first place. Given that the USB A connectors are pretty good at collecting water, I'd go for the latter approach.
Alternatively, cut and splice the cable, or replace the USB connectors with a more waterproof connector (weatherpack or something). But if you don't want to do that, self-amalg or perhaps Sugru would be a good start.
(It's a magic rubbery tape that's tacky but not sticky. You pull the backing off, stretch it and wrap it tightly around the thing you're applying it to. After a day or two, it becomes a solid mass of rubbery stuff rather than layers of tape. If you want it off, attack it with scissors, and you don't have residue like you get with insulating tape.)
