How can I use electronics right below their operating temperatures?
While components and assemblies generally have some operating "margin" outside of their specified temperature ranges, to some extent they will begin to suffer degraded performance, and this may or may not affect what you are trying to do.

So yes, you do need to pay attention to the operating temperature, either by buying items that are specified to work in your temperature range or by providing a temperature-controlled environment for them. Putting them in an enclosure and relying on self-heating can work, but you'll want to monitor the actual temperature in order to make sure.

If the equipment is on continuously, the temperature should remain fairly stable. If the equipment gets turned off and on, then the start-up at low temperatures could become problematic, and the thermal cycling may introduce other problems with mechanical stress and/or condensation. An auxiliary heater may be required.

In small enclosures, a large PTC thermistor can be used directly as both a heating element and a temperature regulator. For larger enclosures, you may need to have a separate heating element and a circuit to control it.