Brihat Samhita
दधिसदृशाग्रो नीलो भानुच्छादी खमध्यगो अभ्रतरुः । पीतच्छुरिताश्च घना घनमूला भूरिवृष्टिकराः ॥ ३०-१८ ॥
If the appearance known as Abhrataru (cloud-tree) should be seen with its ends of the colour of coagulated milk, the body being black, and if it should conceal from view the midday-sun, there will be abundant rain; also if the clouds should appear of beautiful yellow colour and thick at the bottom, the rainfall will be abundant.
english translation
dadhisadRzAgro nIlo bhAnucchAdI khamadhyago abhrataruH । pItacchuritAzca ghanA ghanamUlA bhUrivRSTikarAH ॥ 30-18 ॥
hk transliteration by Sanscript