A Wind Chill Advisory has been issued until tomorrow morning for the following counties, Osceola, Dickinson, OBrien, Clay, Buena Vista, Mitchell, Howard, Winneshiek, Allamakee, Floyd, Chickasaw, Fayette, Clayton, Benton, Buchanan, Delaware, Dubuque, Jones, Linn, Black Hawk, Bremer, Butler, Cerro Gordo, Emmet, Franklin, Grundy, Hamilton, Hancock, Hardin, Humboldt, Kossuth, Marshall, Palo Alto, Pocahontas, Tama, Webster, Winnebago, Worth and Wright. Wind Chills this evening and overnight will approach -20 to -30. Actual readings will fall into the single digits below zero so only a slight breeze will drop wind chills to these dangerous levels. Frostbite can occur in as little as 30 minutes tonight into tomorrow morning.