Abbad bin Tamim narrates from his uncle (may Allah be pleased with him) that he (peace and blessings be upon him) went out for the rain prayer, and he said: He (peace and blessings be upon him) turned his cloak around, placing its right side on his left shoulder and its left side on his right shoulder; then he supplicated to Allah Almighty.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الاستسقاء / 6415