Frank J. Wilstach, comp. A Dictionary of Similes. 1916.

Uncertain

Uncertain as a comet.
—Anonymous

Uncertain as horse flesh.
—Anonymous

Uncertain as weather.
—Anonymous

Uncertain as the wind.
—C. C. Colton

Uncertain as the almanac.
—Jacke Drum’s Entertainment

Uncertain in her temper as a morning in April.
—Sam Slick

Uncertain as a child’s swift moods.
—Arthur Symons

Uncertain as a vision or a dream.
—Alfred Tennyson