The Prophet (ﷺ) went out towards the Musalla in order to offer the Istisqa' prayer and when he intended to invoke (Allah) or started invoking, he faced the Qibla and turned his cloak inside out.
Sahih al-Bukhari Book 15, Hadith 23
← Previous Hadith "The Prophet (ﷺ) went out to the Musalla to offer the Istisqa' prayer, faced the Qibla and offered a two rak`at prayer and turned his cloak inside out." Narrated Abu Bakr, "The Prophet (ﷺ) put the right side of his cloak on his left side."

Sahih al-Bukhari Book 15, Hadith 22 Next Hadith → A bedouin came to Allah's Messenger (ﷺ) on a Friday and said, "O Allah's Messenger ! The livestock, the offspring, and the people have perished." So, Allah's Messenger (ﷺ) raised both his hands invoking Allah (for rain) and the people too raised their hands with Allah's Messenger (ﷺ) invoking Allah (for rain). We had not left the mosque when it started raining. It rained till the next Friday when the same man came to Allah's Messenger (ﷺ) and said, "O Allah's Messenger! The travelers are compelled to postpone their journeys (because of excessive rain) and the roads are overflowed."

Sahih al-Bukhari Book 15, Hadith 24