Is the prayer for rain (Salat al-Istisqa) authentically established (sahih al-thubut)?

The Salatul-Istisqa (prayer for rain) is an established Sunnah, confirmed by the practice of the Messenger of Allah, peace and blessings be upon him, and his Caliphs. The Prophet, peace and blessings be upon him, went out for it, dressed humbly, showing humility and supplication. Then he ascended the minbar, supplicated, prayed humbly, and glorified Allah, then he prayed two rak'ahs just as he prays on Eid.