Hail was a type of weather consisting of large balls of ice which fell from the sky.
In 2268, the poem with which the children of the Starnes Exploration Party summoned Gorgan mentioned hail twice. (TOS: "And the Children Shall Lead")
The Arpasian Range on the planet Ktaris was known for high winds and hail. In 2376, Naomi Wildman mentioned this when showing her science project, a model of Ktaris, to Kathryn Janeway and Chakotay, after the latter commented on the storms she'd depicted in the mountains. (VOY: "Child's Play")