I have recently seen a number of matches where prior to the start of the game heavy rain made the pitch pretty hard to play on. Interestingly some of these matches were postponed (e.g. recent qualifier between Poland - Englad) whereas some others did not (this weeks Champions League match between Galatasaray - Cluj).
In the second case it was pretty obvious that there would be absolutely no quality of football due to the conditions on the pitch due to erratic behavior of the ball on "grass" (terrible bounce, passes getting stuck on puddles, players sliding uncontrollably...)
Now that game reminded me of Euro 2008 match between Turkey and Austria, during which rain had made the game practically impossible for both teams and unexpected ball behavior caused a rather silly goal.
THat being the background, when the refs go out on the pitch to judge whether or not to start the game, what do they look for? Are there specific/descriptive criteria with which they take their decision?