In years past I remember looking out the window as soon as I woke up to see what the weather is like, sad to say these days I usually glance at a smart phone on my bed side table. This way I not only get the current conditions but also the high and low temperature for the day and the precipitation prediction. This project is is doing a similar thing.
This Raspberry Pi Irrigation System Rain Bypass uses a web connected Raspberry Pi to look up rain predictions and disable the irrigation system from watering the lawn if it won’t be necessary. The existing controller has an input for a rain sensor which is how the Raspberry Pi is inhibiting the controller but by having the rain prediction data you could optimize your water usage since if it will rain this afternoon you might want to hold off on watering the lawn in the morning.