Why is the "Dragon Rising" on the second day of February related to the understanding of star movement in ancient astronomy and agricultural solar terms?

In fact, the "Dragon Rising" on February 2 is related to the understanding of star movement in ancient astronomy and agricultural solar terms. After February of the lunar calendar, the "rainy" solar term comes, the lack of rain in winter ends, and the rainfall gradually increases, which is originally the characteristic of the monsoon climate in North China.