The festival of Tiragan is observed on July 1st, and it is primarily a rain festival and it is one of the three most widely celebrated feasts (along with Mihregan and Norooz) amongst Iranian peoples. Tir in modern Persian,; Tishtar in Middle Persian or Pahlavi; and Avestan Tishtrya, is the Yazad presiding over the Star Sirius, brightest star in the sky, and of rain, and thus Tir Yazad especially invoked to enhance harvest and counter drought (Av. Apousha).
Besides an Afrainagan or Jashn dedicated to Tir, there appear to have been many customs associated with Tiragan. Mary Boyce (Persian Stronghold of Zoroatrianism) mentions a game of Moradula ('bead-pot') or chokadula ('fate-pot'). She also related the custom of tying rainbow-colored bands on their wrists which were worn for ten days and then thrown into a stream. She observed during her time in Sharif-abad that many of the charming old Tiragan customs had died away by the 1960's leaving "merry-making by young people and children, who with a happy license... splash and duck one another in the village streams."
Tiragan is also associated with the legend of the arrow ('tir'), which is briefly alluded to in the Tishtar Yasht (Yt8.6):
"We honor the bright, khwarrah-endowed star Tishtrya who flies as swiftly to the Vouru-kasha sea as the supernatural arrow which the archer Erexsha, the best archer of the Iranians, shot from Mount Airyo-xshutha to Mount Xwanwant. For Ahura Mazda gave him assistance; so did the waters ..."
An expanded account is found in Mirkond, History of the Early Kings of Persia, Erekhsha Khshviwi-ishush (Pahlavi Arash-i Shiwatir, i.e. 'Arash of the swift arrow, and in modern Persian, known as Arash-e Kamangir) was the best archer in the Iranian army. When Manouchehr and Afrasiyab determined to make peace and to fix the boundary between Iran and Turan, 'it was stipulated that Arash should ascend Mount Damavand, and from thence discharge an arrow towards the east; and that the place in which the arrow fell should form the boundary between the two kingdoms. Arash thereupon ascended the mountain, and discharged towards the east an arrow, the flight of which continued from the dawn of day until noon, when it fell on the banks of the Jeyhun (the Oxus).'
The following Tirgan story from the Persian Rivayats tie together many of these elements:
It is related that when the wicked Afrasiyab, the Tur, ruled over the country of Iran, it did not rain, at that time, for 8 years. Afrasiyab, the Tur, asked the wise and the astrologers why it was not raining. Zu Tahmasp answered: "You turned faithless, because Faridoun had allotted to you Turkestan (only) and entrusted it to you whereas he had allotted Iran to us and given it to us. You turned away from that covenant and set it aside. It is for this reason that, owing to this sin of yours, it does not rain." Afrasiyab asked how this could be ascertained. Zu Tahmurasp said: "I shall throw an arrow from here, and where my arrow falls, there will be the boundaries (of your territory)." Afrasiyab accepted it and entered into a compact thus: "I shall consent to have as the boundaries (of my territory) that place where your arrow settles and I shall go out of Iran." When this compact was entered into, it was on the day Tir of the month Tir that Zu Tahmasp uttered the name of God and threw the arrow from the country of Iran and that arrow fell in the country of Turan by the command of Lord Ohrmazd. When that arrow settled in the country of Turan, Afrasiyab took this witness that the rains did not come on account of his faithlessness. Then Afrasiyab arose from that place and went out of Iran with his army and settled in the country of Turan. The intelligence of this spread on the day Govad and heavy rains poured down on the day Govad. Then they assented to institute a festival in the country of Iran on the day Tir of the month Tir and up to now the Dasturs of Iran write a Nirang (formula) and tie it on the hands of the faithful and remove it from their hands on the day Govad, throw it into the sea on that day for the reason that the glad tidings of the return of Afrasiyab to Turan had reached on the day Govad. It is for this reason that this nirang is untied from the hands and thrown into the sea so that all calamities may sink into the sea.