Why do devices stop operating properly in extreme cold?
-4 F is -20C, which is a standard low limit for chips and electrical components. Some of that is just because it is very hard to test chips at low temperature, but there are real issues you can run into, which include:


Batteries degrade at low temperatures, depending on their chemistry. 


The battery output voltage is lower, meaning you need more current to get the same power
The battery internal resistance can increase. The added resistance can heat up the board, but it also wastes power and makes the battery output voltage less stable, as it will change with current draw. 
The heat caused by the extra resistance can potentially damage the battery, since you are heating up the inside while the outside is cold, creating a thermal gradient which adds mechanical stress.

Thermal cycling of parts can become worse. Things break when you make them cold and heat them up because of thermal expansion. I believe this issue is worse at lower temperatures, possible related to metals becoming brittle when they are very cold.
Chips can draw more current at low temperatures. This issue compounds the other two, since more current becomes more heat, which increasing thermal cycling.
Chip timing changes. Digital circuits have special timing rules to ensure that all signals are in the right place at the right time. Lowering the temperature changes all that and can create a race condition.