Cargo aircraft temperature
Many things including bottles containing liquids break when the temperature drops below zero, so the cargo hold is always maintained above freezing; 7&deg;C is typical (source).  This applies to both pure cargo aircraft and mixed passenger/cargo airplanes.

That said, it's harder to control for (say) cargo sitting around on tarmac while waiting to be loaded on the plane.  Your cargo shipper can likely arrange temperature-controlled shipping for you, but at a steep extra cost, and this is usually meant for perishables where the main danger is heat, not cold.  But unless you're shipping something to/from Siberia, you'll likely be fine.