How to get higher weight range for vocabulary
Remember to pass value by reference.

function &lt;MYMODULE&gt;_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  if ($form_id == "taxonomy_overview_vocabularies") {
    foreach ($form as &amp;$vocabulary) {
      if (isset($vocabulary['weight']['#delta'])) {
        $vocabulary['weight']['#delta'] = 20;
      }
    }
  }
}