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 m3, or 1 litre of water to each square metre of the field.