it depends on how big the raindrops are, but I would use millilitres. 👍
You would use the metric unit "liters" to measure the capacity of a hot water tank.
The basic metric unit of measure for measuring the capacity of a pitcher is liters (L).
milliliter
Litres.
120 ml
Liters, milliliters.
mililiter
You would use millimeters for the measure of the capacity of a paper cup.
sob
All volumes are measured in litres.
Milliliter
You use litres to measure the capacity of a car's gas tank.