What does 80% in the weather forecast mean?

It means that the probability of precipitation is 80%. According to the information of central weather bureau, 80% of the weather forecast means that the probability of rain in a certain area is 80%, and the probability of rain in the forecast time and area is 80%. Knowing the probability of precipitation in a certain area, people can take countermeasures against rainy weather and reduce the inconvenience in life.