Power tools cannot be used in any type of wet condition regardless of the circumstance. Corded and Cordless tools operate with electricity which do not work in wet conditions. For example, powered sanders should not be used for wet sanding. Using a power tool (cordless or corded) in such conditions may result in shock, personal injury, death, fire and/or property damage.
The only exception would be certain tile saws- which have the necessary design and protection to be used in a wet environment.
Always consult the owner's manual for proper tool use and safety!