Is there a hard requirement for extreme cold or hot environments laid out in acquisition policy anywhere including Army?
Is there a KPP or suggested KSA? Or is it based on OMS/MP only? Or CONOPS?
In the Army it is up to the individual weapon system to determine the temperature range. In theory, it should be determined in the OMS/MP.
JCIDS provides some latitude for the sponsor to write the Sustainment metrics based on the type of weapon system. Temperature extremes are not necessarily part of the reliability KSA/APA but could be.
Since reliability should specify some time period between some type of failure and those failures should be limited to certain environmental conditions.
This is one place that could have temperature ranges defined:
Temperature range could be listed as an APA in section 5 in an attribute such as Operating Environment or it could be listed in a paragraph in section 6, Other System Attributes.