SB 10.20.32

evaṁ nivasatos tasmin
 rāma-keśavayor vraje
śarat samabhavad vyabhrā
 svacchāmbv-aparuṣānilā
Word for word: 
evam — in this manner; nivasatoḥ — while the two of Them were dwelling; tasmin — in that; rāma-keśavayoḥ — Lord Rāma and Lord Keśava; vraje — in Vṛndāvana; śarat — the fall season; samabhavat — became fully manifest; vyabhrā — free from clouds in the sky; svaccha-ambu — in which the water was clear; aparuṣa-anilā — and the wind was gentle.
Translation: 
While Lord Rāma and Lord Keśava were thus dwelling in Vṛndāvana, the fall season arrived, when the sky is cloudless, the water clear and the wind gentle.