MD3 and MD4 Operating temperature

The IQAN-MD4 has a wider temperature range than the IQAN-MD3, so on the MD4, we have not seen any need to add a software function for shutting down the display at extreme temperatures.

Also note that in the MD4 instructions, there are two temperature ranges stated.
http://www.parker.com/literature/Electronic%20Controls%20Division/Literature%20files/IQAN-MD4_instructionbook_HY33-8408-IB_UK.pdf

Ambient temperature -30 to 70 °C, this is the recommended ambient operating temperature.
Storage temperature -40 to 85 °C

What these numbers don't reveal is that especially in low temperatures, it is the storage temperature that is the important number for avoiding damage to the display.

Starting up the display at -40 °C is not really damaging it, but the MD4 display may not be usable until it is > -30°C.

At high temperatures, you will be able to use the MD4 display outside of the operating range, but colors may not be correct. Also, when combining high temperatures (outside of the operating range) with moisture, there can or will be damage to the display.  
The MD4 +70°C is given as the recommended maximum ambient (surrounding) temperature, to have margins to the display component temperature, since component temperature will be higher than ambient.

Does that mean we can store the screen at -50 deg C but wait until it is above -30 to operate it?

No, the storage temperature is -40°C. If you go below storage temperature, there is a risk of freezing the liquid chrystals, which would cause permanent damage.
But you can switch on the MD4 at -40°C. The MD4 will start, but the display won't be readable until the heat geneated gets it to about -30°C.