It really depends on what a high temperature environment is.
As we all know, electronics are prone to underperformance or damage when running at higher than expected temperatures.
This being said, knowing that a light fitting is going to go into a high temperature environment when it is being designed allows it to be created to handle those temperatures.
If an office LED luminaire designed for office ambients, with limited heat sinking behind the LED and a low specification driver was mounted in a high temperature environment, then it is very likely the end user will be disappointed with the results. A shorter than expected life, higher failure rates and lower light output could all be anticipated.
A light fitting designed for purpose with large heat sinking and good thermal management, as well as high specification drivers, will be able to perform in a high temperature environment of 50 degrees centigrade, and maybe higher. Though the effect of temperature should still be taken into account at lighting design stages as lumens and life would still be affected by the increased heat.
There are many products on the market that are designed for high temperature industrial environments.