If your irrigation system is operating during or shortly after a rain event, your irrigation controller is helping you spend money on things you really don't need. The simple fix is to install a rain sensor.
Florida Law (Section 373.62 F.S.), requires all automatic irrigation systems be outfitted with a working rain shut-off device or other technology to inhibit or interrupt operation of the irrigation system during periods of sufficient moisture. To ensure proper operation, sensors should be checked at least once a year. Once every six months is better. Information about types and installation of rain sensing devices is available from the University of Florida.