It means the area received rain that filled up to a height of 30 millimetres in a rain gauge. Rainfall is measured using a rain gauge, which collects rainwater in a cylinder. The height of water collected tells how much rain has fallen.
Class 7 Social Science Textbook Chapter 2 Understanding the Weather Question Answer
Class 7 Social Science Chapter 2 Understanding the Weather Solutions
When the news reports 30 mm of rainfall, it means that rainwater collected in a rain gauge rose to a height of 30 millimetres. A rain gauge is a cylindrical instrument with a funnel that directs rain into a measuring tube. The depth of water collected indicates the amount of rainfall. It’s a precise way to monitor precipitation and helps weather departments track rainy days, issue flood warnings and understand seasonal patterns important for agriculture and water management.
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