Vassa also called Rains Retreat, or Buddhist Lent, is the three-month annual retreat observed by Theravada

Theravada

Theravada ; literally, "the Teaching of the Elders" or "the Ancient Teaching", is the oldest surviving Buddhist school. It was founded in India...

 practitioners. Taking place during the rainy season, Vassa lasts for three lunar month

Lunar month

In lunar calendars, a lunar month is the time between two identical syzygies . There are many variations. In Middle-Eastern and European traditions, the month starts when the young crescent moon becomes first visible at evening after conjunction with the Sun one or two days before that evening...

s, usually from July (the Burmese month

Traditional Burmese calendar

The traditional Burmese calendar is a lunisolar calendar based on both the phases of the moon and the motion of the sun. Within each month of the Burmese calendar, a major festival, often Burmese Buddhist in nature, is held...

 of Waso) to October (the Burmese month of Thadingyut ).

For the duration of Vassa, Bhikkhu

Bhikkhu

A Bhikkhu or Bhikṣu is an ordained male Buddhist monastic. A female monastic is called a Bhikkhuni Nepali: ). The life of Bhikkhus and Bhikkhunis is governed by a set of rules called the patimokkha within the vinaya's framework of monastic discipline...

s remain inside monasteries and temple grounds. In some monasteries, monks dedicate the Vassa to intensive meditation

Meditation

Meditation is any form of a family of practices in which practitioners train their minds or self-induce a mode of consciousness to realize some benefit....

. During Vassa, some Buddhist lay people choose to observe Vassa by adopting more ascetic practices, such as giving up meat, alcohol, or smoking. While Vassa is sometimes casually called "Buddhist Lent

Lent

In the Christian tradition, Lent is the period of the liturgical year from Ash Wednesday to Easter. The traditional purpose of Lent is the preparation of the believer – through prayer, repentance, almsgiving and self-denial – for the annual commemoration during Holy Week of the Death and...

", others object to this terminology.

Vassa is followed by Kathina

Kathina

Kathina is a Buddhist festival which comes at the end of Vassa, the three-month rainy season retreat for Theravada Buddhists. The season during which a monastery may hold a Kathina festival is one month long, beginning after the full moon of the eleventh month in the Lunar calendar .It is a time...

, a festival in which the laity expresses gratitude to monks. Lay Buddhists bring donations to temples, especially new robes for the monks.

The Vassa tradition dates back to the time of the historical Buddha

Gautama Buddha

Siddhārtha Gautama was a spiritual teacher from the Indian subcontinent, on whose teachings Buddhism was founded. In most Buddhist traditions, he is regarded as the Supreme Buddha Siddhārtha Gautama (Sanskrit: सिद्धार्थ गौतम; Pali: Siddhattha Gotama) was a spiritual teacher from the Indian...

. The Buddha didn't want mendicant monks to travel during the rainy season as they may unintentionally harm crops and/or insects during their travels.

Many Buddhists live in regions which don't have rainy seasons and as such, the practice isn't practiced worldwide.