Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 8 · Marriage
विवाहः
अपि सर्वगुणोपेतं दम्पत्योर्मृत्युदं यतः ।अनुक्ताः स्वल्पदोषाः स्युर्विद्युन्नीहारवृष्टयः ॥ ४७८ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 478.
even if it holds every good quality, because it may put the couple's life at risk. The unnamed small faults are lightning, mist and rain.
Simple meaning: Such a day may put the couple's life at risk. Lightning, mist and rain are small faults.
प्रत्यर्कपरिवेषेंद्रचापांबुधरगर्जनाः ।
A false sun, halo, rainbow, thunder and some named faults and days are bad for weddings.
दग्धलग्नांधवधिरपंगुसंज्ञाश्च राशयः ।
Burnt lagnas and the signs called blind, deaf and lame are also faults. Now the rules for them.
अकालजा भवंत्येते विद्युन्नीहारवृष्टयः ।
Lightning, mist and rain out of season spoil a good act. In season they do no harm.