Frostfall is a festival of the fall season.

Frostfall is one of the twenty-four solar terms that occurs around October 23rd of the solar calendar every year, when the sun reaches 210 degrees of the yellow meridian. It is the last of the twenty-four solar terms in the fall season, with the meaning of cold weather and the appearance of the first frost.

The Monthly Seventy-two Waiting Collection: "In the middle of September, the air is clean and condensed, and the dew is frosty". At this time, China's Yellow River Basin has appeared white frost, thousands of miles of fertile land, a silver ice crystals glittering, at this time the leaves are yellow, in the leaves.

Ancient book "twenty-four seasons solution" said: "gas and frost, Yin began to condense also."

It can be seen that "frost" indicates that the weather is getting colder, and frost begins to fall. Meteorology, generally the first frost in the fall is called "early frost" or "first frost", and the last frost in the spring is called "late frost" or "final frost". The last frost in spring is called "late frost" or "final frost". The period between the last and first frosts is the frost-free period.

The early frost is also called "chrysanthemum frost", because at this time the chrysanthemums are in full bloom, the great writer of the Northern Song Dynasty, Su Shi, has a poem: "a thousand trees swept as a yellow, only hibiscus alone fragrant".

China's ancient frost is divided into three waiting: one waiting for the jackal is a sacrificial beast; two waiting for the yellow fall of grass and trees; three waiting for the stinging insects Xian bent. Jackals began to capture prey, sacrificial beasts, beasts and sacrifices to the sky to report this also, the square store and sacrifices the meaning of autumn gold; the leaves on the ground withered and yellowed fall; stinging insects are all in the hole does not move do not eat, hanging down his head into hibernation state.

Frost is made of water, and how is it made of water?

The Southern Song poet Lu Benzhong in the "Nangezi travel thoughts" duck said: "stage invasion slanting moon, stream bridge to the evening frost."

Lu You wrote in "Frosty Moon," "The withered grass is white with frost, and the moon's shadow is new in the cold window."

Indicating that frost appears on a clear moonlit night in autumn. Autumn night without clouds, the ground as uncovered by, heat dissipation a lot, the temperature suddenly dropped to below 0 ° C, by the ground not much water vapor will be condensed in the stream, between bridges, leaves and soil, the formation of fine ice needles, some become hexagonal frost, white and loose structure.

Frost, can only be formed on sunny days, people say "thick frost fierce sun" is the reason.