For rain

Allāhumma ‘asqinā ghaythan mughīthan marī'an murī`a, nāfi`an ghayra ḍārr, `ājilan ghayra ājil. O Allah, shower upon us abundant rain, beneficial not harmful, swiftly and not delayed. Reference: Abu Dawud 1/303. See also Al-Albani SahihAbu Dawud 1/216.
Allāhumma aghithnā, Allāhumma aghithnā, Allāhumma aghithnā. O Allah, send us rain. O Allah, send us rain. O Allah, send us rain. Reference: Al-Bukhari 1/224, Muslim 2/613.
Allāhumma’sqi `ibādaka wa bahā'imak, wanshur raḥmatak, wa aḥyi baladaka ‘l-mayyit O Allah, give water to Your slaves, and Your livestock, and spread Your mercy, and revive Your dead land. Reference: Abu Dawud 1/305. Al-Albani graded it good in Sahih Abu Dawud 1/218.