1, count the reasons for the cold weather:

This is mainly because the total heat budget deficit on the ground only reaches the maximum in April and September, while the heat storage in the northern hemisphere is the least in a year, so it is the coldest. In addition, the cold air mass in Siberia has also developed to a very strong stage during this period, and the frequent invasion of strong cold air is also one of the reasons for the low temperature.

2. Calculation method of nine cold days:

The method of calculating the temperature by number nine is suitable for the areas where the temperature changes obviously from winter to around in China. The calculation of cold and warm changes is accurate to days. Judging from the number of days from winter to Sunday, the coldest periods are "March 9 and April 9", and "September 98 1 day" is the deep spring and warm days. In some places, count to nine from the day of the winter solstice.

In some cold areas, the temperature in winter and spring is below zero degrees Celsius for a long time, and there is no obvious change from winter to around. The morning and evening of the ninth anniversary is not much different from the temperature of a few degrees Celsius. For the convenience of counting nine, counting begins from the date of winter solstice, that is, the date of winter solstice is called "cross nine", every nine days is "nine nine", and so on.

The custom of counting nine in cold weather;

1, drawing 9:

The custom of "painting nine" appeared in some places in the Ming Dynasty. The so-called painting is actually a picture that calculates the warm date of spring after the winter solstice. In addition, the Qing Dynasty also had "99 Poems and Paintings for Eliminating Cold", with four sentences and 36 sentences every nine days. It is an elegant history from "Huang San ruled the world" in ancient times to "sitting in the Qing Dynasty in golden years".

2, write nine:

The custom of "writing nine" appeared in some places in the Qing Dynasty. "Writing Nine" has a strong cultural flavor, and words such as "weeping willows in front of the pavilion and cherishing the spring breeze" or "sending fragrant flowers into the house in the spring vestibule" are often used (of course, traditional). Tick them into a picture first and fill them in from the ninth day (similar to "painting red" in calligraphy practice).

Black with a thick brush, nine strokes per word, one stroke per day, and it takes just 8 1 day to fill in these nine words. Interestingly, after filling in a stroke every day, you have to use a fine brush to record the weather of that day on the strokes. Therefore, a line of "writing nine" is also more detailed meteorological data in the past nine days.