* WHAT...Sub-freezing temperatures as low as 28 degrees expected. * WHERE...All of southern Illinois and southwest Indiana, and portions of southeast Missouri and western Kentucky along and north of line from Van Buren to Sikeston, to Paducah through the Land Between the Lakes to Hopkinsville and Elkton. * WHEN...From 1 AM CDT /2 AM EDT/ to 9 AM CDT /10 AM EDT/ Saturday. * IMPACTS...Frost and freeze conditions could kill crops, other sensitive vegetation and possibly damage unprotected outdoor plumbing.