"of or relating to rain," 1855, American English, from Greek hyetos "rain" (see hyeto-) + -al (1).
Entries linking to hyetal
hyeto-
word-forming element in science meaning "rain," from Greek hyetos "rain," from hyein "to rain," from PIE root *seue- (2) "take liquid" (see sup (v.2)).
-al 1
suffix forming adjectives from nouns or other adjectives, "of, like, related to, pertaining to," Middle English -al, -el, from French or directly from Latin -alis (see -al (2)).