Just use a 'standard' system that looks up the chance of rain and multiplies it - e.g. average 10% chance of rain at that time of year becomes 60%, average of 50% becomes 90%, and then apply the sprinklers automatically based on that, windspeed, etc.
In effect use a computer rain simulator (as in GP4 for example) but connected to the sprinkler network. 'Random' rain that favours nobody, and is out of direct control of the FIA.