Sayyiduna Abdullah bin Zayd (may Allah be pleased with him) says that the Prophet (peace and blessings be upon him) supplicated for rain while he (peace and blessings be upon him) was wearing a black garment. He (peace and blessings be upon him) intended to take hold of its lower part and put it on top, but when he (peace and blessings be upon him) grew tired he placed it over his neck. The wording of both (narrations) is the same.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الاستسقاء / 6417