Minor Heat

Meaning

Minor Heat, Xiaoshu, is the eleventh of the twenty-four solar terms: the Sun at 105°, about 7 July. The heat has come but is not yet at its height; that is for the next term, Major Heat. In the Yangtze valley the plum rains end around now and the dry, bright heat of high summer takes over.

It is an opening term: it opens the Goat month, the sixth solar month and the last of summer, whose branch, Wei, is an Earth branch and the storehouse of Wood. The season that began with Wood’s growth and rose to Fire now begins to turn towards the harvest.

Its three pentads are the warm winds arriving, the crickets taking shelter in the walls, and the young hawks learning to strike. In the same weeks the hottest stretch of the year, the dog days, begins, counted from the solstice by the days of the sixty-cycle.

In practice

• In BaZi a birth from this instant belongs to the Goat month and its pillar; a birth within five minutes of it is marked uncertain, since a slightly different time would give the Horse month.
• In Chinese astrology the month animal turns from the Horse to the Goat, and the Cycles lens begins the Goat month’s reading here.
• In Feng Shui the month’s star changes, one less than the Horse month’s.
• The Calendar marks it on its day, with the Sun at 15° Cancer, as the opening of the Goat month; the dog days begin on the third Geng day after the solstice, which the day’s stem shows.

Across traditions

• In ancient Rome the dog days, dies caniculares, were named for Sirius, the Dog Star, rising with the Sun in July and August; China’s sānfú fall in the same weeks, counted by the stems of the days instead of a star.
• In Japan summer greeting cards, shochū mimai, are sent from around shōsho until risshū, asking after friends in the heat; in Korea the term is soseo, in Vietnam tiểu thử.
• In Western astrology the Sun is at 15° Cancer, the middle of the first summer sign, a fortnight after the solstice.

Origin and history

The term and its three pentads come from the oldest lists, the Huainanzi’s of 139 BC and the seasonal instructions before it. The dog days are older still as a custom: Sima Qian’s Shiji records that Duke De of Qin first kept the fú days in 676 BC, and the count from the Geng days after the solstice has set them ever since, the first, middle and last fú, ten days or more each.

In many villages Minor Heat was the time to taste the new rice, offering the first of it to the ancestors before eating; families set out books and clothes to air in the sun in these weeks, a habit that the old almanacs tie to the sixth month.

How Ulune calculates it

Ulune takes Minor Heat as the instant the Sun’s apparent longitude reaches 105°, from its table of the solar terms computed with the Swiss Ephemeris for 1800 to 2200. The Goat month and its pillar begin at that instant, whatever the clock or the time zone. In 2026 it fell on 7 July at 01:56 UT.

Correspondences