Pride of the Morning
That early mist or shower which promises a fine day. The Morning is too proud to come out in her glory all at once- or the proud beauty being thwarted weeps and pouts awhile. Keble uses the phrase in a different sense when he says:
Pride of the dewy Morning, The swain's experienced eye From thee takes timely warning, Nor trusts the gorgeous sky.
Keble: 25th Sunday after Trinity.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894