What Is the Buddhist Rainy Season? Understanding the Vassa and Kaṭhina Ceremonies Each year, Theravāda Buddhist monks all over the world make a determination to stay in a single monastery for a three month period of the Rainy Season also known as Vassa, or the Rains Retreat. You will hear the term “Vassa” often in this article, so please remember it. Traditionally, it starts the day after the Full Moon Day in July or the day after the Āsāḷha full moon known in the Pāḷi language. If your monks move around a lot and you need to rely on a teacher, you can expect the monks to stay at a monastery for a full three months without moving around. Some make determinations to practice harder, while others who already follow a steady practice simply continue their daily routine as usual. In this article, we will look at the origins of Vassa, the different types of Vassas, the allowances to leave the vassa on business, or by emergencies, if it affects the age of a monk, and what happens at the end of Vassa.