How do weather sensors in modern controllers improve water efficiency?

• A. They adjust irrigation based on rainfall, temperature, and ET data, reducing unnecessary watering.
• B. They increase irrigation during hot days to maintain plant color.
• C. They only log weather data for records.
• D. They shut off irrigation during cloudy days regardless of data.

Answer: (A)

Weather sensors in modern irrigation controllers let the system respond to real conditions instead of sticking to a fixed schedule. They measure rainfall, temperature, humidity, and solar radiation to estimate how much water plants actually need, using evapotranspiration (ET) as a guiding metric. The controller then adjusts run times and cycles so watering matches the amount lost through ET and recent precipitation, avoiding unnecessary watering after rain or on cool, damp days. This targeted approach reduces waste, minimizes runoff and leaching, and helps keep plants healthy by supplying water only when they need it. Choices that suggest watering more on hot days, only logging data, or turning off irrigation based solely on cloudy conditions miss the core idea that the controller uses real-time weather data to modulate irrigation.