Water always finds a way to be in the wrong place at the wrong time. At least when it comes to electric motor and drive reliability. Moisture settling on the insulation of your electric motor will reduce the resistance-to-ground and increase the capacitance-to-ground readings. These facts are well known. Not as well known, is the fact that a poor ground wall insulation condition can also be detrimental to the operation, reliability, and life expectancy of your variable frequency power supply.
Source PDMA Corporation