For many decades, the Avestan common noun apaosha- "drought" was thought to derive from either *apa-uša- "burning away" or *apa-vṛt(a)- "stemming the waters.
Ahura Mazda then himself offers sacrifice to Tishtrya, who now strengthened reengages Apaosha in battle at noon and conquers the demon of drought.
This legend has been interpreted to be a mythological conflation of a seasonal and astronomical event: The heliacal rising of Sirius (with which Tishtrya is associated) occurred in July,[a] just before the hottest and driest time of the year.
A mythological explanation of the heliacal setting of Sirius is only alluded to in the Avesta: In Yasht 18.5-6,[3] Apaosha is contrasted with the bringers of prosperity, that is, Tishtrya and his assistants Vata and Khwarrah.
On the opposing front, Tishtrya is supported by Verethragna (→ Vahman), Haoma (→ Hom), Apam Napat (→ Burz), the hordes of the fravashis and by the Vayu (→ Weh).