Canto 3 -
Araṇya-kāṇḍa
Chapter 16: Lakṣmaṇa’s Description of Winter
Text 3.16.12
निवृत्ताकाशशयनाः पुष्यनीता हिमारूणाः।
शीता वृद्धतरायामास्त्रियामा यान्ति साम्प्रतम्॥
nivṛttākāśa-śayanāḥ puṣya-nītā himāruṇāḥ
śītā vṛddhatarāyāmās triyāmā yānti sāmpratam
nivṛtta-ākāśa-śayanāḥ = one can no longer sleep under the open sky; puṣya-nītāḥ = while the nights approach the month of Pauṣa; hima-aruṇāḥ = and are filled with snow; śītāḥ = and filled with cold air; vṛddhatarāyāmāḥ = longer; triyāmāḥ = the nights; yānti = will become; sāmpratam = now.
Now the nights will become longer and filled with cold air. One can no longer sleep under the open sky while the nights approach the month of Pauṣa and are filled with snow.1
1 The Vedic month Pauṣa generally occurs between December and January.
Nivṛttākāśa-śayanāḥ indicates that during winter nights, one cannot sleep directly under the moonlight and so on.