Power management for a 5V 12A load
If you're not comfortable working with mains voltage, and assuming that your loads are in the same enclosure as your power supply (i.e. you're generating a lot of heat in an enclosure), you might consider a AC->DC power supply mounted remotely from your enclosure, and running 5V into your enclosure.

Normally, voltage droop would be a concern under such use cases, as it only takes 0.04 ohm of line resistance to drop 10% of your supply voltage.  Many power supplies have remote sense leads, such that the power supply closes its control loop around the supply voltage at your enclosure, compensating for any transmission losses.

The benefits of this approach include reduced power dissipation in your outdoor enclosure and only hand-friendly 5V in the enclosure (but watch out for shorts!).  The downsides are the need for a separate (hopefully indoor-rated) enclosure for the supply and possibly a slightly higher cost for a AC-DC supply with remote sense capability.