Valmiki Ramayana Aranya Kanda Sarga 23 Shloka 7

प्रभिन्नगिरिसङ्काशाः those looking like shattered mountains, तोयशोणितधारिणः clouds bearing bloodlike water, भीमाः most frightening, वलाहकाः clouds, तत् that, आकाशम् sky, अनाकाशम् other than the sky, चक्रुः rendered.

The clouds looked like shattered mountains pouring down bloodlike rain which filled the sky and made it appear frighteningly different.