What natural phenomenon indicates that it will rain?

1, the sky: the air humidity becomes higher, the air pressure decreases, the sky is dark, the clouds are densely covered, and sometimes lightning flashes and thunders.

2. Ants can move: ants digging holes in the ground think that it will flood when it rains, that is, they will run away before it rains.

3, flying insects fly low: before the arrival of rain, the air humidity will greatly increase, the air pressure will be significantly reduced. The moisture in the air will condense on their wings, which will become heavier and swallows will fly low to catch insects.

4. Small fish will float to the surface to breathe: the air pressure in the water is low and there is little dissolved oxygen, so the fish will float to the surface to breathe.

5, earthworm out of the hole: the ground is wet and soft, and the earthworm will climb out of the ground, indicating that it will rain.

Several precursor clouds before summer rain

Hook cloud, which the masses call "hook cloud". It floats horizontally in the sky like a wisp of silk, with the cloud upward and a small hook at one end. The color of the cloud is milky white and bright. Generally, it appears before the influence of cold air in the north or low pressure at high altitude. This cloud has appeared, and it will rain soon. Therefore, there is a saying that "clouds hook raindrops".

Cirsium japonicum, people call it "Fish Scale Day". It usually appears in the blue sky. Small white clouds, arranged neatly and closely, rippling like fish scales, are very beautiful. The duration after formation is short, usually only a few minutes, and more than an hour. Its appearance shows that there is a trough of low pressure approaching over the local area, which is a sign that sunny days turn cloudy and rainy days. Therefore, there is a saying that "it's a fish scale day, it's windy and it doesn't rain".

Flocculent cumulus clouds are called "cotton clouds" by the masses. It also often appears in the clear sky in summer, like clusters of scattered and broken cotton wool, and also like a burst of cotton. Clouds vary in size and height. It is formed under the condition of extremely unstable humid air, so the cloud is fragmented and a symbol of rain. Therefore, the agricultural proverb says, "There are cotton clouds in the sky, and there will be a thunderstorm soon."