The 24 solar terms, 二十四節気(niju-shi-sekki) in Japanese, was created by people in ancient China, based on the position of the sun in the zodiac.
A year is devided to 4 seaons, and each season is devided to 6. The new circle starts from Risshun (the beginning of spring).
A website (*1) says that this is created by farmers to guide the agricultural affairs and farming activities.
Although it doesn't reflect observable reality of Japanese season, we still often use the terms to indicate seasons, and have traditional events and customs.
The dates written is in 2018 -2019. They change slightly in each year.
立春(Risshun) - the beginning of spring. -Feb 4
雨水(U-sui) - rain water - It gets warmer, and the snow changes to the rain.-Feb 19
啓蟄(Kei-chitu) - awakening of insects - Hibernating Insects under the ground are awake. -March 6
春分(Shun-bun) - the vernal equinox-March 21
清明(Sei-mei) - clear and bright - Everything is alive and looks pure.-April 5
穀雨(koku-u) - grain rain - It has a light rain which moisten grain. -April 20
立夏(Rikka) -the beginning of summer. -May 5
小満(Sho-man) -small full - Everything grows gradually and reaches at the certain size. -May 21
芒種(Bo-shu) -Grains with 芒(a kind of spikes) such as rice and wheat are planted.-June 6
夏至(Ge-shi) - the summer solstice -June 21
小暑(Sho-sho) -minor heat - Wet season finishes and it starts to be hot. -July 7
大暑(Tai-sho) - extreme heat, the hottest period-July 23
立秋(Risshu) - the beginning of autumn. -August 7
処暑(Sho-sho) - limit of heat. - The weather is said to start cooling down.-August 23
白露(Haku-ro) - white dew - White dew drops wet grass.-September 8
秋分(Shuubun) - autumnal quinox -September 23
寒露(Kan-ro) - cold dew- Autumn season deepens, and cold dew drops stay on wild grass.-October 8
霜降(So-ko) - frost descent -October 23
立冬(Rittou) - the beginning of winter. -November 7
小雪(Sho-setsu)-minor snow - It gets colder, and the rain becomes the snow.-Nobember 22
大雪(Tai-setsu) - major snow - The snow starts to lie thick.-December 7
冬至(To-ji) - the winter solstice -December 22
小寒(Sho-kan) - minor cold, the beginning of coldness -January 6, 2019
大寒(Dai-kan) - major cold, the coldest season - January 20, 2019
1. 木村吉隆 著 「江戸暦 江戸暮らし」 亜紀書房 2013年
(`Edo koyomi Edo kurashi` by Yoshitaka Kimura Publisher Aki Shobo in 2013 )
2. https://www.chinahighlights.com/festivals/the-24-solar-terms.htm (*1)