Product ambient temperature ratings and testing

[Eric_the_EE]

I am in the process of testing an electronic device for min/max ambient operating temperatures. Currently, the device is operating in an environmental chamber at the rating extremes, but I'd like to learn more about how others verify temperature ratings. Proof of test is required, so I cannot just use the temperature rating of the weakest component in the BOM.
In particular, I've been looking for an IEC/EN standard that specifies test parameters and execution for a given rating.
For example, if my product is rated for 70 Celsius at 85% RH, what temperature and RH should I test at? How long should the test be? What is professional verification of the rating?

Anyone know of any standards that address this? What temperature verification methods do you use?

[Eric_the_EE]

Post update.
After digging a while longer through commercial test reports and the IEC web store, I found some standards that I will be referencing for my application.
Maybe these notes will help someone else someday looking for similar info. 

IEC-61131-2:2017 Industrial-process measurement and control – Programmable controllers – Part 2: Equipment requirements and tests. Specifically, the test will fulfill the requirements for Table 4 - Dry-Heat Withstand Test and Table 5 – Cold Withstand Test.

IEC 60068-2-1, Environmental testing – Part 2-1: Tests – Test A: Cold
Specifically, the test will be completed with severity (temperature and duration of exposure) specified in section 6.6.1 Temperature and section 6.6.2 Duration.

IEC-60068-2-2, Environmental Testing – Part 2-2: Tests – Test B: Dry Heat.
Specifically, the test will be completed with severity (temperature and duration of exposure) specified in section 6.5.2 Temperature and section 6.5.3 Duration.