Brihat Samhita
गिरयो अञ्जनचूर्णसन्निभा यदि वा बाष्पनिरुद्धकन्दराः । कृकवाकुविलोचनौपमाः परिवेषाः शशिनश्च वृष्टिदाः ॥ २८-०६ ॥
If mountains should appear black like collyrium, if the caves should be felt very warm or if the lunar halo should appear like the colour of the eye of the cock, there will be immediate rain.
english translation
girayo aJjanacUrNasannibhA yadi vA bASpaniruddhakandarAH । kRkavAkuvilocanaupamAH pariveSAH zazinazca vRSTidAH ॥ 28-06 ॥
hk transliteration by Sanscript