If it's an option, you could consider running heat in your rig for that day or two of extreme low temps, provided you have the enclosed underbelly and what is referred to as "heated tanks/underbelly.
Other wise I think you will have to at least drain the water and blow the lines out. This is what is used for that along with an air compressor set at 40to45#
Blow-out Plug - Camco 36104 - Winterizing - Camping World
If you have liquids in the holding tanks and can't dump them, then you better pour a few gallons of RV anti freeze in each one. Amount you pour in will be determined by how much liquid is in the tanks.
Good luck.
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