What does the weather forecast mean by 70%?

It means that there is a 70% chance of precipitation. According to the query of China Meteorological Bureau, the percentage in weather forecast usually refers to the precipitation probability or relative humidity, and the precipitation probability refers to the percentage of the possibility of precipitation in a certain period of time. A 70% weather forecast means that there is a 70% chance of precipitation. Weather forecast is a pre-estimation and prediction of future weather changes.