When are the days long and the nights short?

Long days and short nights are from the vernal equinox to the autumnal equinox, usually from March 20th to September 22nd.

On the vernal equinox, the sun shines almost directly on the equator of the earth, and the whole world is almost as long as day and night. After the vernal equinox, the direct point of the sun began to enter the northern hemisphere, and the days became longer and the nights became shorter in all parts of the northern hemisphere. Vernal equinox is an important solar term.

It not only has astronomical significance, but also has obvious characteristics in climate. At the vernal equinox, China has entered a bright spring except the Qinghai-Tibet Plateau, the northeast, the northwest and the northern part of North China. On the vast land, willows are green, Fei Ying grass grows, wheat jointing and rape blossoms.

Extended data:

The vernal equinox also has obvious characteristics in climate. At this time, the climate is mild, the rain is abundant and the sun is shining, and the wintering crops in most parts of China enter the spring growth stage.

In addition to the Qinghai-Tibet Plateau, Northeast China, Northwest China and North China, China has entered a beautiful spring. The significance of the vernal equinox, first, refers to the equal division of day and night, each of which is 12 hours; Second, the vernal equinox is in the middle of spring (from beginning of spring to Changchun), and the spring is equally divided.

During the spring equinox and solar terms, the East Asian trough is obviously weakened, and the trough ridge activity in the westerly belt is obviously enhanced. From Mongolia to the northeast, there are often low-pressure activities and cyclone development. Low-pressure movement causes cold air to go south, and it is windy and windy in the north. When the long wave trough moves eastward, there will be continuous rainy and cold weather due to the intersection of cold and warm air masses.