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

Cool

Cool as a snow bank.
—Louisa M. Alcott

Cool as a November twilight.
—Anonymous

Head as cool as an usurer’s.
—Anonymous

Cool as a dog’s nose in a wire muzzle.
—Josh Billings

Cool as a deep river
In shadow.
—Rupert Brooke

Cool down like a dish of tea.
—Colley Cibber

Cooled, like lust in the chill of the grave.
—Ralph Waldo Emerson

Cool as a cucumber.
—John Gay

Cool as the silent shades of sleep.
—Robert Herrick

Cool as a moonbeam on a frozen brook.
—Oliver Wendell Holmes

Cool as the pool that the breeze has skimmed.
—Thomas Hood

Cool as the call of a wind on the still of the sea.
—Richard Hovey

Cool as aspen leaves.
—John Keats

Cool … like a cutlass blade.
—Amy Lowell