* WHAT...Temperatures as low as 33 will result in frost formation. * WHERE...Huron, Lenawee, Livingston, Macomb, Monroe, Oakland, Sanilac, St. Clair, Washtenaw, and Wayne Counties. * WHEN...From 3 AM to 8 AM EDT Saturday. * IMPACTS...Frost could harm sensitive outdoor vegetation. Sensitive outdoor plants may be killed if left uncovered. Take steps now to protect tender plants from the cold.