I had some years ago a 25 euros Quickcam outside, it was time before wx-stuffing, it hadn't any proper shield, just a quickly built box of wood and a plexi as "window" so it wasn't weatherproof in any way, just so it not get wet when rained. Anyway it was out in temps below -20 C and in snowstorms and worked just fine

Also my last weather-cam has been working ok in temps around -15 C, will be intresting to see how the new one (Canon Powershot) goes this winter

I think the humidity can be a bigger problem than the temperature itself for them.
Henkka