Yahweh prepared a great fish to swallow up Jonah, and Jonah was in the belly of the fish three days and three nights.
And in the very next line, Jesus went on to mention the queen of the south who would rise up in judgment and condemn the generation of the Pharisees, "For she came from the ends of the earth to hear the wisdom of Solomon; and, behold, a greater than Solomon is here"  (Matthew 12:42).  The only logical deduction that may be made from this statement is that Christ considered Jonah just as historical as the queen of the south.