The proverb every cloud has a silver lining means that every difficult or sad situation has a comforting or more hopeful aspect, even though this may not be immediately apparent—cf. also the pessimistic reversal every silver lining has a cloud.

In 1840, the Irish novelist known as Mrs S. C. Hall (Mrs Samuel Carter Hall, née Anna Maria Fielding – 1800-81) published Marian; or, A Young Maid’s Fortunes. In April that year, The Citizen; A monthly Journal of Politics, Literature, and Art (Dublin, County Dublin, Ireland) published a review of this novel (Katty Macane is Marian’s friend):

As Katty Macane has it, “there’s a silver lining to every cloud that sails about the heavens if we could only see it,” and so it proved with Marian. When all hope seemed gone, her prospects brighten; she is discovered by a Lady Isabella Gascoigne—who was attracted by her in her childhood—and taken under her protection, along with Katty.

The Athenæum, Journal of Literature, Science, and the Fine Arts (London, England) of 29^th February 1840 had also published a review of Mrs S. C. Hall’s novel:

Katty Macane constantly looming in the distance to cheer the distressed girl with her untiring affection and her unvarying prophecy, that “every cloud has its silver lining.”

This is the earliest attestation of the current form of the proverb. Interestingly, this reviewer quoted a phrase that does not appear in the novel: the only expression that Katty Macane uses is there’s a silver lining to every cloud. But the very fact that this reviewer unintentionally replaced it with every cloud has its silver lining shows that the latter was already in usage at that time.

The epigraph to the novel is this quote from John Milton:

                                        Did a sable cloud
Turn forth her silver lining on the night?

This is because the image of the silver lining of a cloud appears to have been created by the English poet John Milton (1608-74) in Comus. A Mask Presented at Ludlow-Castle, 1634 (sable means black, and silver lining denotes the light of the moon shining from behind the cloud):

(ed. Cambridge University Press, 1906)
I see ye visibly, and now beleeve
That he, the Supreme good, t’whom all things ill
Are but as slavish officers of vengeance,
Would send a glistring Guardian, if need were
To keep my life and honour unassail’d.
Was I deceiv’d, or did a sable cloud
Turn forth her silver lining on the night?
I did not err, there does a sable cloud
Turn forth her silver lining on the night,
And casts a gleam over this tufted Grove.