Our recorders and accessories are rated for use to -20 °C (-4 °F). Temperatures below this may damage the equipment. At temperatures below freezing you can expect the display to become sluggish, have low contrast or go out altogether. Batteries will have a greatly reduced life at colder temperatures; check the datasheet for the batteries you are using for an estimate of the magnitude of this reduction.
For terrestrial recorders, storing the unit in an insulated cooler or even burying it will help protect against short-term temperature swings, but not against sustained temperatures below -20 °C.