What is the name of the Zoroastrian summer festival?

The Zoroastrian summer festival is called Tirgan.

Tirgan is an ancient Iranian festival associated with Zoroastrian tradition and celebrated in early summer. It falls on Tir 13 in the Iranian calendar, usually corresponding to July 2, 3, or 4, although calendar systems and regional observances can shift the modern date.

Water is the festival's best-known feature. Celebrants may splash one another, reflecting traditions connected with rain, fertility, and purification. Dancing, poetry, special foods, and colorful wristbands are also associated with Tirgan; in some customs, the bands are worn for several days before being cast into a stream.

Tirgan is linked with Tishtrya, the star deity identified with Sirius, and with the heroic archer Arash. Iranian legend says Arash shot an arrow to establish the boundary between Iran and Turan, while the Avesta's Tishtrya hymns connect the festival season with rain-bringing cosmic struggle.

Tirgan is distinct from Nowruz, the spring New Year festival; Mehrgan, associated with autumn; and Sadeh, the midwinter fire festival.