**1mm rainfall means**every one square meter area

**is**filled with the water of height

**1mm**.

**1**square meter = 1000mm length ×1000mm breath. So

**1mm rain means**1000mm length × 1000mm breath ×

**1mm**height = 1litre of water. Every square meter has one litre of water.

How much rain in an hour is a lot?

Moderate

**rainfall**measures 0.10 to 0.30 inches of**rain per hour**. Heavy**rainfall**is more than 0.30 inches of**rain per hour**.**Rainfall**amount is described as the depth of water reaching the ground, typically in inches or millimeters (25 mm equals one inch). An inch of**rain**is exactly that, water that is one inch deep.How much water is 1 mm of rain?

In terms of volume, with a rainfall of 10 mm, every square metre of the field receives

**0.01 m**, or**10 litres**, of rain water. With a rainfall of 1 mm, every square metre receives 1 litre of rain water. A rainfall of 1 mm supplies**0.001 m**, or 1 litre of water to each square metre of the field.^{3}