The 24 solar terms are a group of 24 traditional divisions of the solar year, established in the Zhou Dynasty (1045-256 BC).

Rain Water is the first solar term of the traditional Chinese calendar. It usually begins on the 5th of February in the Gregorian calendar, when the sun reaches the celestial longitude of 315 degrees. At this time, the rain water starts to flow in the middle and lower reaches of the Yellow River, the Huaihe River, and the Yangtze River, and marks the start of the spring ploughing season.