The solar term in beginning of autumn in 221 is at 14: 37 on August 7th, 221 (June 29th of the lunar calendar)

1. Climatic characteristics of beginning of autumn: beginning of autumn, precipitation humidity and other factors are the turning point of the year, and the precipitation humidity is constantly decreasing. After entering autumn, in nature, the qi of Yin and Yang began to change, everything began to grow from lush to mature, and the climate began to transition from rainy and humid in summer to dry and rainy in autumn. Seasonal changes, rainfall, dry humidity and other changes in the southern region are obvious; From the temperature point of view, "beginning of autumn" is often still in the middle of the day.

2. About the origin of beginning of autumn

(1) beginning of autumn is the 13th solar term among the 24 solar terms, and the first solar term in autumn, which falls on August 7-9 of the Gregorian calendar every year. At this time, the bucket handle of the Big Dipper points to the southwest, and the sun reaches 135 longitude. The 24 solar terms reflect the change of "Qi" in the four seasons. beginning of autumn is the node where the yang gradually closes and the yin gradually grows, and the yang gradually turns into yin. Beginning of autumn, which also means precipitation and humidity, is at the turning point of the year and tends to decline or decrease; In nature, everything began to grow from lush to mature.

(2) beginning of autumn doesn't mean that the extremely hot weather is over. beginning of autumn is still in the summer heat period, but it doesn't come out until the second solar term in autumn, and the weather is still very hot in early autumn. The so-called "heat is in three volts", and it is also called "falling after autumn", and there is at least "falling" hot weather after beginning of autumn. According to the calculation method of "dog days", the day of "beginning of autumn" is often still in mid-dog days, that is to say, the heat is not over, and the real coolness usually comes after the solar terms of the Millennium. The watershed between heat and cool is not in the solar term in beginning of autumn.