اللّهُمَّ اسْقِنَا غَيْثاً مُغِيثاً مَرِيئاً مَرِيعاً، نَافِعاً غَيْرَ ضَارٍّ، عَاجِلاً غَيْرَ آجِلٍ
Allaahumma 'asqinaa ghaythan mugheethan maree'an maree'an, naafi'an ghayradhaarrin, 'aajilan ghayra 'aajilin.
O Allah, shower upon us abundant rain, beneficial not harmful, swiftly and not delayed.

(Aameen Yah Robb).