The National Weather Service has issued a Frost Advisory effective from 4 until 8am Monday for the following counties, Pocahontas, Humboldt, Wright, Franklin, Butler, Bremer, Sac, Calhoun, Webster, Hamilton, Hardin, Grundy, Black Hawk, Crawford, Carroll, Greene, Boone, Story, Marshall, Tama, Audubon, Guthrie, Dallas, Cass, Adair, Adams, Union, Buchanan, Delaware, Dubuque, Benton, Linn, Jones and Jackson. Temperatures will drop to around the freezing mark in these locations allowing frost to form. If you have sensitive plants outdoors, make sure you either cover them up or bring them in.