A smart irrigation system for an irrigation controller associated with an irrigation site is described herein. The smart irrigation system comprises a central control system having a user interface and a smart scheduler. The central control system is configured to derive and send an irrigation schedule for the irrigation. The smart scheduler comprises a data receiver, a processor, and a signal interface. The data receiver is configured to receive the irrigation schedule. The processor is configured to convert the irrigation schedule to a series of control signals that the irrigation controller recognizes. The signal interface is configured to connect to the irrigation controller and to send the series of control signals to the irrigation controller. The system uses weather data and irrigation site-specific information to automatically apply the optimal irrigation schedule. User are able to remotely control the irrigation via networks such as Internet.