Rainfall refers to the total amount of rainfall per unit time, so what does the weather forecast mean? For example, from moderate rain to heavy rain, does it mean the total amount?

I think your question involves two concepts, rainfall and rainfall intensity. Of course, it's all about time. Rainfall refers to the total rainfall per unit time, while small to moderate to heavy rain refers to the gradual increase of rainfall intensity over time, that is to say, in unit time, rainfall increases, with light rain: 1-2.5 mm, and the rainfall in any 6 minutes does not exceed 0.3 mm; Moderate rain: 1 hour rainfall is more than 2.5 mm, but not more than 8 mm, or the rainfall in any 6 minutes is not more than 0.8 mm; Rainstorm: 1 hour precipitation 8 mm, I hope it will help you.