Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 11 · Rain, Kurma Chakra, Utpata
वृष्टिः कूर्मचक्रम् उत्पाताश्च
वर्षाप्रवेशे शशिनि जलराशिगतेपि वा ।केंद्रगे वा शुक्लपक्षे चातिवृष्टिः शुभेक्षिते ॥ ७२१ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 721.
Take the time the rains begin. The Moon may be in a water sign. Or it may be in a kendra (corner house) in the bright half. If good planets see it, there is very heavy rain.
Simple meaning: The Moon in a water sign, or in a corner house in the bright half, seen by good planets, brings heavy rain.
अल्पवृष्टिः पापदृष्टे प्रावृट्कालेऽचिराद्भवेत् ।
Bad planets seeing the Moon bring little rain. The same holds for the Moon with Venus.
प्रावृषींदुः सितात्सप्तराशिगः शुभवीक्षितः ।
In the rains, the Moon in these places can bring more rain.
सद्यो वृष्टिकरः शुक्रो यदा बुधसमीपगः ।
Venus close to Mercury brings quick rain. The Sun between them can stop the rain.