And rain fell upon the earth: rain translates a word that is used here for the first time in Genesis and whose meaning is a heavy rain. So also 8.2; 1 Kgs 17.1, 7; Psa 68.9. Many languages distinguish between various kinds of rain according to the season, quantity, accompanying wind, and other factors. The rain in verse 12 is heavy, continuous, and can be destructive. Anchor Bible translates “heavy rain” here.

For forty days and forty nights, see verse 4. The nonstop nature of the rain is emphasized here; one translation brings this out with “continued for forty days and forty nights—it didn’t let up at all.”

The falling of the rain actually followed the events reported in verses 13-16. In those languages where narrative must keep strictly to time sequence, it will probably be necessary to move some or all of verse 12 down to the end of verse 16. Another solution is to consider verse 12 as parenthetical, as New Jerusalem Bible does. Mundhenk (1994) suggests that, since the time sequence is not moved forward with the mention of forty days and forty nights, we may translate, for example, “… the windows of heaven were opened, and the rain began that would fall for forty days and nights.”

Quoted with permission from Reyburn, William D. and Fry, Euan McG. A Handbook on Genesis. (UBS Helps for Translators). New York: UBS, 1997. For this and other handbooks for translators see here .