As salamu alaykum warahmatullahi wabarkatuhu...
INVOKING ALLAH FOR RAIN( Istisqaa)
Narrated 'Abdullah bin Dinar:
My father said, "I heard Ibn 'Umar reciting the poetic verses of Abu Talib: And a white (person) (i.e. the Prophet) who is requested to pray for rain and who takes care of the orphans and is the guardian of widows." Salim's father (Ibn 'Umar) said, "The following poetic verse occurred to my mind while I was looking at the face of the Prophet (p.b.u.h) while he was praying for rain. He did not get down till the rain water flowed profusely from every roof-gutter: And a white (person) who is requested to pray for rain and who takes care of the orphans and is the guardian of widows . . . And these were the words of Abu Talib."
When there is loss of famine and when there is no rain...the salah is offered which is known as istisqaa...