Glum is the sky, by night imprisoned,
As over it the dark clouds creep,
Not menacing or wistful is it,
But plunged in dreary, torpid sleep.
Alone the streaks of lightning, bursting
Through cloud and shadow, seem to be,
As they flare up and blaze, conversing
Like deaf-mute demons soundlessly.

As at a signal, for an instant
A strip of sky is lit, and Lo! -
From out the murk the forests distant
Emerge, set suddenly aglow.
But the light dies, the darkness fleeing
That cloaks the startled, wakeful sky,
And all is still... Is a plot being
Hatched in the silent wastes on high?..

Fyodor Ivanovich Tyutchev

http://www.poemhunter.com/poem/gum-is-the-sky/