Photos of abused MCU's
Any "harsh environment" will destroy a stock Arduino.  They utterly lack any sort of protection.

A company I used to work for would get warranty returns for vehicle data computers that were half filled with water but still fine electrically as the board was conformal coated with a silicone resin.

In any case, outside of temperature swings (and occasionally, radiation), the MCU does not, nor is expected to, survive.  It is the job of enclosures and coatings to protect it from everything else, such as moisture, chemicals, and thermal shock.