Brihat Samhita
चैत्रसितपक्षजाताः कृष्णे अश्वयुजस्य वारिदा गर्भाः । चैत्रासितसम्भूताः कार्तिकशुक्ले अभिवर्षन्ति ॥ २१-१२ ॥
Clouds that conceive in the bright half of Caitra (March and April) will be delivered of rain in the dark half of Aśvayuja and those that conceive in the dark half of Caitra will be delivered in the bright half of Kārttika (October and November).
english translation
caitrasitapakSajAtAH kRSNe azvayujasya vAridA garbhAH । caitrAsitasambhUtAH kArtikazukle abhivarSanti ॥ 21-12 ॥
hk transliteration by Sanscript