Here's why:
* Predicate: The predicate tells us what the subject does or is.
* Subject: The subject is "It".
* Verb: The verb is "shivered".
* Prepositional Phrase: "In the wind" modifies the verb "shivered" and adds detail to the action.
Therefore, the complete predicate includes the verb and any words that modify it, making "shivered in the wind" the complete predicate.