It's really up to YOU, or whomever else is dictating the product requirements, to decide which environment the thing must...
- A. Survive in, and
- B. Remain functional in.
Those may be different values. For example, a standard LCD is not much use below 0C since the liquid becomes too sluggish to react to the applied voltages. However it will work when it warms up. If however you take it down to -40 the liquid can actually freeze and destroy the unit.
However, the above range is also dependent on installation location. Direct sunlight, proximity to other heat sources, poor ventilation, etc. can drastically change those numbers.
What you enclose your electronics inside also matters. The electronics inside an unventilated black box left on the dashboard in the sun in Death Valley, USA, may reach temperatures hot enough to melt some devices.
In addition, you ALSO need to worry about the enclosure itself. If it is that black box I mentioned above, it has to be made of a material that will not melt, crack or degrade in sunlight. It must also be constructed in such a way that it can expand and contract without stress failure.
Sometimes extreme conditions are required. Military specification tend to be much more extreme than domestic, but wider examples exist. For example, devices to be used outside in Antarctica, or a device that will be installed next to a blast furnace. In those cases extraordinary measures need to be taken. Heaters need to be added to the box for the cold example, and liquid cooling piped to the latter from a more distant location.
For automotive applications it really depends on what the device does. If it is critical to the safe operation of the vehicle, e.g. a brake sensor, it needs to work better than the low levels of the standards, perhaps as low as -60°C. If it is that little display the kids watch "Sponge Bob" on in the back seat, 0°C to +50°C may be sufficient.
The automotive "standards" indicate...
Where cost goes from high for Grade 0 to low at Grade 4. You have to decide which one of those you need to beat for the functionality of your design and to be within your cost budget.