Hang up the tree when the wind blows.

A wind of level 6 or above is called gale.

In the weather forecast business in China, the wind with a wind force of 6 or above is called gale, which can overturn ships, trees, telephone poles and houses, cause coastal storm surges and fuel fires. Gale weather mainly occurs in spring and summer, mainly thunderstorm and gale. July and August have the highest frequency, followed by April and May, and there are relatively few strong winds in autumn and winter.

cause

Wind is a kind of air flow phenomenon on the earth, which is generally caused by solar radiation heat. Sunlight shines on the earth's surface, causing the surface temperature to rise, and the surface air to expand and become lighter and lighter.

After the hot air rises, the cold air with low temperature flows in horizontally, and the rising air falls down because it gradually cools and becomes heavier. Because the surface temperature is high, it will heat the air and make it rise. This airflow is the wind.