It uses hyper-local weather data and zone parameters.
With Sprinkler Plus, you can create Smart Schedules which automatically water your plants when needed.
To do this, we measure water in (from rain and running your irrigation system) and water out (evapotranspiration), along with previous and forecasted weather to calculate the water balance in each zone. When the balance is forecasted to reach the allowed depletion (dry out), we schedule a watering.