Supplication for rain (Istisqa)

اللَّهُمَّ اسْقِنَا غَيْثاً مُغِيثاً مَرِيئاً مَرِيعاً, نَافِعاً غَيْرَ ضَارٍّ, عَاجِلاً غَيْرَ آجِلٍ

(O Allah, send upon us helpful, wholesome and healthy rain, beneficial not harmful rain, now, not later.)

Source: Abu Dawud 1/303.

اللَّهُمَّ أَغِثْنَا, اللَّهُمَّ أَغِثْنَا, اللَّهُمَّ أَغِثْنَا

(O Allah, relieve us, O Allah, relieve us, O Allah, relieve us.)

Source: Al-Bukhari 1/224, Muslim 2/613.

اللَّهُمَّ اسْقِ عِبَادَكَ, وَبَهَائِمَكَ, وَانْشُرْ رَحْمَتَكَ, وَأَحْيِي بَلَدَكَ الْمَيِّتَ

(O Allah, provide water for Your servants and Your cattle, spread out Your mercy and resurrect Your dead land.)

Source: Abu Dawud 1/305.