I base my watering on previous and expected rainfall.
I use a kind of ‘weighting’ to allocate a value to each figure then do a calculation of the numbers to produce a final figure.
If that figure is below a certain number I’m told by HE to water the garden 
Another user uses then same calculation to turn on his water...
[RELEASE] - Irrigation Switch App - Turns on a switch if you need to water the garden
Andy
