<?php
function replace_core_jquery_version() {
wp_deregister_script( 'jquery' );
// Change the URL if you want to load a local copy of jQuery from your own server.
wp_register_script( 'jquery', "https://code.jquery.com/jquery-3.1.1.min.js", array(), '3.1.1' );
}
add_action( 'wp_enqueue_scripts', 'replace_core_jquery_version' );