Sunan Ibn Majah Book 34, Hadith 63
“Allahumma inna na’udhu bika min sharri ma ursila bihi (O Allah, we seek refuge with You from the evil of that with which it is sent).” Then if it rained he would say: “Allahumma sayyiban nafi’an (O Allah, a beneficial rain),” two or three times. And if Allah dispelled it and it did not rain, he would praise Allah for that.
“The Messenger of Allah (ﷺ) used to say” – and (one of the narrators) ‘Abdur-Rahim said: “he used to seek refuge” – “when he traveled: ‘Allahumma inni a’udhu bika min wa’tha’is-safar, wa ka’abatil-munqalab, wal-hawri ba’dal-kawr, wa da’watil-mazlum, wa su’il-manzari fil-ahli wal-mal (O Allah, I seek refuge with You from the hardships of travel and the sorrows of return, from decrease after increase, from the prayer of the one who has been wronged, and seeing some calamity befall my family or wealth).’” (One of the narrators) Abu Mu’awiyah added: “And when he returned he said likewise.”
“Allahumma aj’alhu sayyiban hani’an (O Allah, make it a wholesome rain cloud).”