Frostfall (one of the twenty-four solar terms) Frostfall contains the meaning of the weather getting cold and the appearance of the first frost.

Frostfall, one of the twenty-four solar terms, every year around October 23rd on the Gregorian calendar, the frosty season contains the meaning of the weather is getting cold, the first frost appeared, is the last solar term of autumn, also means that winter is about to start. Frost season, health care is particularly important, there is a folk proverb "a year to make up through, not as good as make up the frost", see the impact of this festival on people.

Frost is water gas condensation, water gas how to condense into frost? The Southern Song poet Lu Benzhong wrote in "Nan Ge Zi - Travel Thoughts": "The stage invades the slanting moon, the stream bridge to late 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." It shows that frost appears on a clear moonlit night in autumn.

There are no clouds in the autumn night, the ground as uncovered by the quilt, a lot of heat dissipation, the temperature plummeted to below 0 ℃, not much water vapor by the ground will condense in the creek between the bridge, leaves and soil, the formation of fine ice needles, and some of them become hexagonal frost flowers. Frost, can only be formed on sunny days, people say "thick frost fierce sun" is the reason. There is a "frost" poem Yun: "when the autumn dew into frost, a few condensation a few Yang. Lotus defeat thousands of pools of depression shore, cotton white hectares of harvest busy."