What is the definition of "millimeter" in weather forecast?

The meteorological department calls it rain and snow precipitation, and precipitation is called precipitation. The unit of precipitation is usually millimeters. 1mm precipitation refers to the water depth per unit area1mm.

/kloc-how much of the 0/mm precipitation fell into the fields? As we know, the area per mu is 666.7 square meters, so the precipitation of 1 mm is equivalent to an increase of 0.667 cubic meters of water per mu. Every cubic meter of water is 1000 kg, so the precipitation of 1 mm is equivalent to watering about 650 kg of water per mu. According to the measurement, the rainfall of 5 mm can make the dry land soak for 3 ~ 6 cm.