Praise be to
Allah.
Offering prayers for rain (salaat al-istisqa’) is Sunnah, as confirmed by saheeh hadeeths and the practice of the early generations of
Islam. Ibn Qudaamah said:
Prayer for rain is a confirmed Sunnah, proven by the
practice of the Messenger of Allah (blessings and peace of Allah be upon him)
and of his successors (the caliphs – may Allah be
pleased with them).
End quote from al-Mughni,
2/148
Abu Dawood
(1165), at-Tirmidhi (558), an-Nasaa’i
(1506) and Ibn Maajah
(1266) narrated that Ishaaq ibn
Abdillah ibn Kinaanah said: al-Waleed ibn ‘Uqbah, who was the governor
of Madinah, sent me to ask Ibn
‘Abbaas about the prayer of the Messenger of Allah
(blessings and peace of Allah be upon him) for rain (istisqa’).
He said: The Messenger of Allah (blessings and peace of Allah be upon him) went
out wearing modest clothes, walking humbly and beseeching Allah, until he
reached the prayer place, where he ascended the minbar,
but he did not give a khutbah like this khutbah of yours; rather he continued to offer supplication
(du‘aa’), beseech Allah and recite takbeer, then he prayed two rak‘ahs
as he used to pray at Eid.
Classed as hasan
by al-Albaani in Saheeh
Abi Dawood, etc
See also the answer to question no. 26167
And Allah knows best.