Because of the grand scale miracles in the Book of Jonah, not least being kept alive in a big fish for three days and three nights, some skeptics and critics deny their historicity and have therefore concluded that the Book of Jonah is either meant to be interpreted as an allegory or a parable.
Whether we interpret it as an allegory (parable) or not, we know that Jonah was an actual historical person who had a prophetic ministry among the northern tribes during the reign of Jeroboam II (ca. 793-753 B.C.); and we know that Jesus referenced Jonah to rebuke the Pharisees and to point to his own death, burial, resurrection, and future judgment (Matthew 12:39-41 and Luke 11:29-32).
Those, like myself, who accept the historicity of the Book of Jonah, views Jesus’ references to Jonah not as an allegory or a parable but as an actual historical account. Moreover, the God who created ex nihilo, parted the Red Sea, shut the mouth of lions, turned water into wine, multiplied a lad’s box lunch of two fish and five loaves, to feed some five thousand and counting, Why couldn’t perform the same sort of miraculous feats we encounter in the Book of Jonah? In the end, like I always tell a fellow theologue and sparring partner, as a biblical absolutist (a term I borrowed from Doug Wilson), to date, I’ve found no reason to doubt the historicity of Jonah. Have you?