Here, a speaker watches the rain grow heavier on a cloudy night and realizes their love for someone is growing in the same way. The comparison is simple and direct: the harder the rain falls, the more the feeling swells, until it is "pouring out" with no holding back.
The word "pouring" carries the poem. It does double duty, describing the weather and the speaker's emotions at once, so the two blend together. Love here isn't calm or quiet. It feels overflowing, almost beyond control, as if the speaker can't contain it any more than a cloud can hold its water.
The mood is tender and a little wistful. The cloudy night and the short, gentle lines make it feel intimate, like a private confession. We don't learn who "you" is or whether the love is returned, and that gap leaves the poem open. It simply captures one moment of strong feeling, matched by the weather outside.