TL;DR: Vũ Thủy (雨水) is the second of the 24 solar terms and the mid-month qi of the first lunar month, beginning when the Sun reaches 330° of ecliptic longitude. In Vietnam time, from 1949 to 2100 it always begins on February 18 or 19, lasts nearly 15 days, and gives way to Kinh Trập on March 5 or 6 (March 4 in a few years late in the 21st century). In 2026, Vũ Thủy begins at 22:45 on February 18, exactly the second day of Tết. The name refers to the time when snow melts into rain water and the weather turns warmer and damper.
What Is the Vũ Thủy Solar Term and Why Is It Called the Damp Solar Term?
Vũ Thủy (雨水) is the second solar term in the 24 solar term system of the old Eastern calendar. The name combines two Han characters: "vũ" meaning rain and "thủy" meaning water. In the common understanding, Vũ Thủy marks the period after Lập Xuân, when the weather begins to warm, snow and ice melt into water, and light rain and drizzle appear more often. This is when heaven and earth shift from dry cold to damp, creating conditions for plants to sprout.
The book Tuế thời quảng ký (歲時廣記) by Trần Nguyên Tịnh, of the Southern Song, places Vũ Thủy under the first lunar month (孟春月) in volume 1 and quotes Lưu Hâm's Tam thống lịch: "立春為正月節雨水為正月中氣雨水者言雪散為雨水也", meaning Lập Xuân is the solar term of the first month, Vũ Thủy is the mid-month qi (trung khí) of the first month, and it is called Vũ Thủy because snow breaks up into rain water[1]. The same entry quotes the Chu thư Thời huấn, which divides the term into three five-day periods: "雨水之日獺祭魚後五日鴻雁来後五日草木萌動", meaning on the first day the otter lays out fish as if making an offering, five days later the swan geese return, and five days after that grasses and trees begin to sprout[1].
When Does Vũ Thủy Start and How Long Does It Last?
Vũ Thủy begins when the Sun reaches 330° of ecliptic longitude and ends when the Sun reaches 345°, when Kinh Trập begins, so each year it lasts nearly 15 days (about 14 days and 22 hours). In Vietnam time, from 1900 to 2100 Vũ Thủy begins on February 18 or 19; February 20 occurs in only 16 years, from 1903 to 1948. Kinh Trập usually begins on March 5 or 6, so the last day of Vũ Thủy is usually March 4 or 5.
According to Thanh Niên newspaper, Vũ Thủy in the Bính Ngọ year 2026 begins on February 18, 2026 (the second day of Tết Nguyên đán) and lasts until March 4, 2026 (the 16th day of the first lunar month)[2]. Kinh Trập follows the very next day, March 5, 2026[3]. Tết Nguyên đán 2026 falls on February 17, so the first day of Tết is still within Lập Xuân, while the second day of Tết has already entered Vũ Thủy.
| Solar term | Solar longitude | Usual Gregorian dates | Main features |
|---|---|---|---|
| Lập Xuân | 315° | February 3 to 5 | Start of spring, still cold |
| Vũ Thủy | 330° | February 18 or 19 | Damp rain, ice melts, soil warms |
| Kinh Trập | 345° | March 5 or 6 | Insects wake after winter |
| Xuân Phân | 0° | March 20 or 21 | Day and night nearly equal |
Start times of Vũ Thủy and Kinh Trập from 2025 to 2030, in Vietnam time:
| Year | Vũ Thủy begins | Time | Kinh Trập begins |
|---|---|---|---|
| 2025 | February 18 | 16:58 | March 5, 15:01 |
| 2026 | February 18 | 22:45 | March 5, 20:49 |
| 2027 | February 19 | 04:32 | March 6, 02:36 |
| 2028 | February 19 | 10:20 | March 5, 08:24 |
| 2029 | February 18 | 16:08 | March 5, 14:12 |
| 2030 | February 18 | 21:58 | March 5, 20:01 |
Why Is Vũ Thủy Not Fixed on the Lunar Calendar?
Solar terms are calculated by the Earth's position on its orbit around the Sun, not by the Moon's cycle as the lunar calendar is. Each solar term corresponds to a 15° arc on the ecliptic, starting from the Xuân Phân point (0°). Therefore, the Gregorian date of Vũ Thủy is fairly stable, while its lunar date changes from year to year. From 1900 to 2100, the start day of Vũ Thủy falls in the first lunar month in 200 of 201 years, at the earliest on day 1 and at the latest on day 30; only in 2034 does it fall on the 30th day of the twelfth month, one day before Tết.
Many people think Tết Nguyên đán is tied to Lập Xuân, but in fact it is the other way round. The lunar calendar orders its months by the mid-month qi: the eleventh month is the one containing Đông Chí, and a leap month is a month without a mid-month qi, so the first month is almost always the month containing the mid-month qi Vũ Thủy, and the first day of Tết is the new moon day (no moon) that opens that month. Lập Xuân does not decide the date of Tết: in 2025 Tết fell on January 29, before Lập Xuân (February 3); in 2026 Lập Xuân fell on February 4, before Tết (February 17).
What Customs Does Vũ Thủy Have?
In Vietnamese folk tradition, Vũ Thủy is not a major festival with its own rituals like Tết Nguyên đán or Tết Trung Thu. However, because this term falls in the first lunar month, it is tied to the Tết atmosphere and early spring activities. People usually notice Vũ Thủy through weather phenomena: drizzle, rising humidity, gradually warming weather. In agriculture, this is an important time to prepare the soil and sow the spring crop.
Among Chinese books, the Tuế thời quảng ký records no custom for the start day of Vũ Thủy; the closest is the entry "飲雨水", quoting the Bản thảo: "正月雨水夫妻各飲一杯還房獲時有子神助也", meaning that if husband and wife each drink a cup of first-month rain water and then retire to their room, they will have a child with the help of the gods[1]. This is a Chinese custom recorded by a Song-era book, not part of Vietnamese custom.
How Does Vũ Thủy Affect Weather and Health?
During Vũ Thủy, air humidity rises noticeably, and average temperatures gradually increase compared with Lập Xuân. In northern Vietnam, this is a period of prolonged drizzle and damp weather, and floors and walls are prone to mold. In southern Vietnam, February and March are the middle of the dry season, so the term's name, "rain water", does not match the weather there.
Regarding health, damp weather and day-night temperature differences make colds common; keeping the house dry and dressing warmly enough are the usual ways of adapting.
What Role Does Vũ Thủy Play in the 24 Solar Terms?
Vũ Thủy is the second of the 24 terms, following Lập Xuân and paving the way for Kinh Trập, Xuân Phân, Thanh Minh, and Cốc Vũ. In the agricultural calendar, it is the time to prepare the soil for the new crop after Tết. In Bát Tự, the Dần month pillar begins at the moment of Lập Xuân; Vũ Thủy is a mid-month qi, so it does not change the month pillar, and people born before or after the start of Vũ Thủy still belong to the Dần month.
The order of Vũ Thủy before Kinh Trập has not always been so. Vương Phu Chi (Wang Fuzhi), in his Chu Dịch bại sớ, notes "古歴惊蛰正月中", meaning the old calendar made Kinh Trập the mid-month qi of the first month. The Tam mệnh thông hội (volume 2, section 论四时节气) explains the present order through the hexagram qi: the first month corresponds to the hexagram Thái, "天气下降，当为雨水" (heavenly qi descends, so it should be rain water); the second month corresponds to Đại Tráng, with thunder above heaven, "当为惊蛰" (so it should be the waking of insects); hence "先雨水而后惊蛰，亦宜也", it is fitting that Vũ Thủy comes before Kinh Trập.
Common Misunderstandings About Vũ Thủy
A common misunderstanding is that Vũ Thủy is "the day the rainy season begins". In fact, Vũ Thủy is only a weather marker and does not determine the rainy season. The main rainy season in both northern and southern Vietnam usually begins around April or May, more than two months after Vũ Thủy.
The second misunderstanding is that Vũ Thủy always falls on the second day of Tết. From 1900 to 2100 there are only 5 such years: 1958, 1977, 2026, 2045, and 2083; in other years Vũ Thủy falls on another day of the first lunar month, except for 2034 mentioned above.
The third misunderstanding is assigning spiritual meanings to Vũ Thủy such as "bad day" or "taboo day". Day-selection books such as the Hiệp kỷ biện phương thư only use Vũ Thủy as a reference point for calculation, for example "雨水後立夏前宜取魚" (from after Vũ Thủy until before Lập Hạ, it is suitable to catch fish), and do not list the start day of Vũ Thủy as a day to avoid. Solar terms are tools for measuring time and weather, not a system for evaluating good or bad.
Nhật Nguyệt's Suggestions
To know when Vũ Thủy begins this year, use the table of start times above; the times are in Vietnam time, so readers in other countries need to convert them to local time. Farmers can use this marker to check soil moisture and prepare seeds. Those studying the calendar can compare the start of Vũ Thủy with the date of Tết each year to see why the first lunar month is the month containing this mid-month qi.
