What does 30% in the weather forecast mean?

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

Terms commonly used in weather forecast:

Sunny day: the cloud cover in the sky is less than 30%.

Yin: The amount of clouds in the sky accounts for more than 90%.

Fog: A large number of tiny water droplets or ice crystals float in the air near the ground, and the horizontal visibility drops below 1 km, which affects transportation.

Light rain: the daily precipitation is less than 10 mm.

Heavy rain: the daily precipitation is 25.0-49.9mm..

Thunderstorm: Intermittent precipitation accompanied by lightning and thunder.

Hail: With the violent vertical movement in the cumulonimbus cloud, small hail nuclei repeatedly rise, condense, fall and melt, and grow into small ice cubes with transparent layers, which have an impact on crops.

Freezing rain: raindrops freeze on the ground below 0℃, also known as rain song (frozen by fog drops, called rime), which often falls off the power lines, freezing the road surface and affecting communication, power supply and traffic.

Sleet: The temperature near the ground is slightly higher than 0℃, and wet snow or rain and snow drop at the same time.

Xiaoxue: The daily snowfall (melting into water) is less than 2.5mm. ..

Medium snow: the daily snowfall (melting into water) is 2.6-4.9 mm.

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