The Tibetan term is khrus bab dus chen (ཁྲུས་འབབ་དུས་ཆེན།): khrus = bathing rite, bab = descent, dus chen = festival. The focus is purification of body, speech, and mind through bathing and Dharma practice. The literal meaning of ཁྲུས་འབབ (khrus ’bab) is derived from its components: ཁྲུས (khrus) refers to a ritual bathing, ablution, or purification bath, while འབབ (’bab) means descent, to fall, or to pour down, as in the context of rain. Thus, the term translates literally as "descent of ablution" or "purifying/bath water falls." In its specific Bhutanese usage, where it is known as Thrue-bab, it signifies the auspicious falling or descent of lustral water used for purification.

Originally, the name Thrue-bab does not directly refer to rain. Therefore, the common English translation, “Blessed Rainy Day,” is not a direct translation.

One folk explanation describes Thrue-bab as the time when water completes its cycle and returns to its sources. Astrologers, however, provide a detailed explanation based on celestial events. They note that during the eighth Bhutanese month, the sun enters Virgo and for a period shines directly upon the star Rishi.

This star is associated with the sage Agastya, one of the seven Vedic rishis. In Himalayan astrology, the star Rishi is said to be composed of crystal and a gemstone with purifying properties. It is known as the medicinal star.

The light emitted from Rishi is believed to cleanse water of impurities and pathogens. Water touched by this light is thought to gain healing qualities, such as being cool, clear, and soothing. The Sowa Rigpa medical tradition recommends using this water to treat illness and support health.

Today this observance, which typically falls in early autumn, signals a seasonal shift. Its core purpose, however, is inner purification. The day serves as a communal reminder to cleanse the mind of defilements and to renew intentions for wholesome action.

In Bhutan, observance begins at dawn on the appointed day. At the precise time set by astrologers, people collect water to be kept as “blessed water” for the year. Many bathe at this moment, sometimes infusing the water with medicinal herbs. The act of outer bathing supports the inner aspiration to purify body, speech, and mind.

The day is also marked by prayer. Recitations of Avalokiteshvara’s mantra, Om mani padme hum, for compassion, and the Medicine Buddha mantra for healing are common. Homes are cleaned, shrine water bowls are replaced, and offerings of light and incense are made. It is a day for family gatherings, picnics, and acts of charity.

For those interested in observing the day, the practice can be adapted to one's own tradition. The essential elements are intention and mindfulness. One might begin by cleaning their space and setting an intention for purification. At the key moment, bathing can be a mindful practice, with the thought: “As this water touches me, may obscurations be washed away for all beings.” This can be followed by recitation, offerings, and dedication of merit.

The spirit of Thrue-bab is embodied by the Brahmaviharas. It is a day to extend loving-kindness to all beings, to express compassion through action, to rejoice in the good fortune of others, and to reflect on impermanence with equanimity.

As with any observance rooted in Vajrayana tradition, specific rites and astrological timings are best confirmed through a qualified teacher or local monastic community. The central invitation of Thrue-bab, however, is universal: to use the element of water as a support for cleansing the heart and mind.