Arduino board safe temparature operating range?

If installing an Arduino board with enclosure, what are the safe temperature operating ranges for the commercially available Arduino boards? I don't see this information typically discussed in the product pages linked from http://arduino.cc/en/Main/Boards.

The target environment can see both hot and cold weather, e.g. -50 C to 50 C.

The arduino chip is rated for operation at -40°C to 85°C according to the data sheet.

There is an internal temperature sensor in Atmega328p.

See ATMega328 datasheet page 261-> 23.8 Temperature measurement