Interesting fact: Just 1 millimeter of rain falling on 1 square meter equals 1 liter of water, which makes rainfall easy to turn into weight.
The answer: Rain weighs 1 kilogram per square meter for every millimeter that falls. So a 10-millimeter rain event over 1 square meter weighs 10 kilograms, and heavier storms add up quickly over large areas.
Rain is one of the easiest natural phenomena to weigh because rainfall depth converts directly into water volume and mass. The challenge is scale: a light shower over a city can still represent thousands of tons of water. Knowing rain's weight matters for flood forecasting, drainage design, agriculture, reservoir management, and stormwater engineering.
