The main thing I'd be worried about is mains voltage - you don't want that anywhere near water!

The receiver itself runs totally from 12v - inside, there's the PSU and 4 wires (2 ground, 2 power) running to the main board.

In theory, you could remove the mains PSU, recase it somewhere else (or use another 12v psu) and just run 12v out to the receiver. For full volume you need something like 3.5A at 12v.

This would make it a lot safer to use outdoors; the backlight runs at ~2kV but it's very low current and hard to touch (ie, behind the front plastics).

I don't think you'd have any temperature issues beyond LCD contrast when very cold or hot. External PSU and some sort of waterproofing is probably the best option.

Hugo