On the fifteenth day of the first lunar month, there is a sentence before the snow lights up the lanterns. On the fifteenth day of the first lunar month, clouds cover the moon.

These two sentences are traditional rural folk songs. Clouds cover the moon on August 15th, and snow lights on the 15th day of the first lunar month next year. This heralds a good year in the coming year. The reason is precisely because there is a corresponding rhythmic relationship between the weather. Rhythm means that after a certain kind of weather appears, the corresponding weather will appear in the next few days.

Clouds cover the moon on August 15th

The length of this rhythm varies. The more commonly recognized ones are 30 days, 60 days, 90 days, 120 days, 150 days, 180 days and It varies from 240 days to 240 days. According to the lunar calendar, "clouds cover the moon on the fifteenth day of the eighth month, and snow lights up the lights on the fifteenth day of the first lunar month", which is exactly the rhythm of 150 days. Historical data has verified that whenever clouds cover the sky, it is cloudy or it rains on the Mid-Autumn Festival, it will be cloudy or snowing on the fifteenth day of the first lunar month of the following year.

Snow lights up on the 15th day of the first lunar month

"Clouds covering the moon" and "snow lighting up lights" appear to be echoes of clouds and snow, but are actually two cold air events In other words, if there is cold air activity before and after the Mid-Autumn Festival, it will cause the phenomenon of "clouds covering the moon". Then, around the Lantern Festival, cold air will invade again, forming a "snow lighting up" situation. Therefore, the proverb "clouds cover the moon on the 15th day of August, and snow lights up the lights on the 15th day of the first lunar month" is a reflection of the rhythmic activity of the cold air that invades China for about five months. Based on this proverb, many meteorological stations have studied the rhythmic relationship of cold air activity for about 5 months, and used it for long-term weather forecasting, and achieved good results; the weather on other days also has this rhythmic relationship, but it has not been used yet. It's just generally noticed by people. The echoing relationship between festival weather is a manifestation of atmospheric rhythmic activities.