Quick answer: A rain sensor tells the irrigation controller to suspend or interrupt scheduled watering after enough rainfall has been detected. Its job is to prevent unnecessary irrigation during or after rain; it does not diagnose leaks, measure every area of soil, or correct poor sprinkler coverage.
Rain sensor versus weather-based controller
A traditional rain sensor reacts to rainfall at the property. A weather-based controller may use broader weather information and programmed site characteristics to adjust watering more dynamically.
Why sprinklers sometimes still run in the rain
The sensor may be bypassed, improperly adjusted, obstructed, disconnected or no longer functioning correctly. Controller configuration can also affect sensor behavior.
Why the sensor matters
Skipping unnecessary watering after rainfall can reduce runoff and water waste while preventing an automatic schedule from watering simply because a start time arrived.
See how rain sensors work and how weather-based controllers can save water.
