The runway is wet. How do you know? Because you are told so. How does the ATCO know to tell you? Because an Ops person has told him. How does the Ops person know? Because the ATCO gave him permission to drive onto the runway to have a look. How long ago was it since the Ops person looked at the runway surface condition and how long after that did it take to pass the info to ATC? Once ATC had the info, how long after that was it that ATC gave you this info. What happened during this time period to the wind and the rain and the level of water on the runway?
Are you getting the thought that the decisions you make about take-off and or landing are not based on factual up to date info? Good
If the RWY is really just WET WET WET, then your departure or landing should not be a problem. Assuming that the equipment that measures the instantaneous wind, last highest gust and trend are accurately calibrated you will have no problem.
Think Swiss cheese, think James Reason and the ask yourself "How did I get here" Hmmn, Not so simple eh?
Sir George Cayley