Do you want to know when it will rain in the future in a clear sky? Here are several precursor clouds before the rain.
Hook cirrus clouds, the masses call "hook hook clouds". It floats across the sky like a bundle of silk, with the clouds facing upwards, a small hook at one end (pictured), and the clouds are milky white and translucent. It generally occurs before the influence of cold air in the north or low pressure at high altitude. Such clouds have appeared and will soon be raining. Therefore, there is a saying that "hooks the clouds and rains".
Cirrocumulus, people call it "Fish Scale Heaven". It generally appears in azure skies. Small white clouds, neatly arranged and tight, resemble the fine scales of a fish, but also like ripple microwaves, very beautiful (pictured). After formation, the duration is short, generally only a few minutes, more than an hour or so. Its appearance indicates that there are low-pressure troughs moving closer over the local area, which is a sign of a transition from sunny to rainy days. Therefore, there is a saying that "the fish scales the sky, and the wind is not rainy".
Flocculent high cumulus clouds, the masses called "cotton clouds". It also often appears in the clear summer sky, like a cluster of scattered and broken cotton wool, but also like a burst of cotton. Cloud sizes vary, with varying heights (pictured). It is formed under extremely unstable conditions of humid air, so the cloud is fragmented and is also a symbol of the rain that will fall. Thus the agricultural proverb says, "There are cotton clouds in the sky, and soon thunderstorms will sound."
The above three kinds of clouds, as long as any one of them appears, generally rain within 1-3 days. If combined with the specific meteorological factor changes at that time, the date of precipitation can be reported more accurately. ( Author: Xiang Lingshan Source: Network Synthesis)
Transferred from China Meteorological Science Popularization Network
Source: Qianxi Southwest Meteorology