The second 節気 “sekki” division of the traditional Japanese calendar is:
The first of the three “kō” microseasons within this division is:
“tsuchi no shō uruoi okoru”
Rain moistens the soil
That makes 土脉潤起 the fourth microseason of the year!
It typically lasts 19~23 February.
This is #4 in a regular subseries of 365 Days of Japanese, where every five or six days I post about a Japanese microseason that has begun around the same date as the entry. I am taking all information from the list of 72 in this article. There is also a 36 microseason list here, which may be more authentic (rather than being based primarily on Chinese sources).
Image credit: This Medium article about the scent of rain.