The rain poured down.

[sania-baharat]

1. It poured all day.
2. The rain poured down.

What is the difference between the sentences above?

 

[tedmc]

1 could mean anything (other than rain) which poured the whole day. Or it could mean it rained heavily the whole day.

2 merely says it rained heavily.

 

[Skrej]

No native speaker would interpret #1 as anything other than rain.

The only difference between the two is the duration. The first one tells us the heavy rain lasted all day. The second one just tells us that it rained heavily for an unspecified amount of time.