A year was divided into 24 solar terms on the traditional Japanese calendar.
Usui is (雨水) literally meannig “rain water” is the 2nd term. It usually begins around February 19, the time when the rain changes to snow and when the Sun is exactly at the celestial longitude of 330°. In the Koyomi Binran (the Handbook of Japanese Calendar) published in the Edo period, it is written that the air gets warm and snow melts into rain water on this day.

Usui falls on the latter half of the month of tiger on the Junishi (zodiac animals) calendar. As the character representing tiger in old writing system was 寅, and it resembles 演 meaning “performing,” Usui is considered to be the time to perform something to express one’s own assertion, which arose in the previous month of Risshun.

In some parts of the country, the first strong south wind of the year blows and Japanese nightingales begin to sing. Farmers start preparing for their agricultural work around this day.