It's hard to say really, while I doubt you'll have an issue with only a few hours in the teens, it is still technically possible.
One option, if you're willing, is to shut off the valve between your FW tank and your water pump, then open your low point drains, draining the lines mostly. The damage to pipes comes not from the freezing itself, but the inability for the water to expand as it freezes. By at least draining the lines you're providing room for that expansion.
The one downside I see to this is that you're losing the water you have in your lines. Since you're dry camping, in a dessert none the less, that may be a precious commodity.
Oh, almost forgot, also bypass your hot water tank so you don't accidentally drain that too. The HW tank shouldn't freeze, since it'll be full of hot water so leaving it full shouldn't be a problem.
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