Why does the weather forecast use precipitation probability?

First of all, if it is raining or snowing, the percentage number next to the raindrop or snowflake icon represents the probability of rain or snowfall.

Second, if it is sunny or cloudy, there is no such percentage.

This kind of weather forecast using probability has been used since 1966 in the United States, 1980 in Japan and 1995 in China. There is also a more elusive word-precipitation probability is often mentioned. Forecasters often broadcast on TV that the probability of precipitation today is 70%. This precipitation probability means that the probability of rain in a certain area is 70%.

Extended data

Rainfall probability

1, the general situation of precipitation probability forecast is sunny, and the probability of 0% is impossible to precipitation; Sunny to cloudy, the probability of precipitation is between 10%-20%, and the possibility of precipitation is very small;

2, cloudy, with sporadic precipitation or local precipitation, when the probability is between 30% and 50%, there is a chance of precipitation;

3. The probability of precipitation is between 60% and 70%.