Just to close a request in order someone will need a right answer from WD support department.
WD Internal hard drives maximum internal temperature is equal to the maximum environmental operating temperature. This information is only valid for WD internal storage drives, because WD External Storages have lower Environmental Operating Temperature due to the enclosure. However most WD External Storages have WD Internal Storage drives inside.
For example:
WD Caviar Green WD40EZRX
http://www.wdc.com/wdproducts/library/SpecSheet/ENG/2879-800026.pdf
Environmental Operating Temperature 0 to 60 °C Maximum internal temperature for this model equals 60 °C. This information is not open source and not specified on WD website, however I have previously already made an escalation to WD Head Department and received this confirmation.
My Book 3.0 External Desktop USB-drive WDBFJK0040HBK has WD Caviar Green drive inside, so the maximum internal temperature of internal drive in My Book is also 60 °C.
