* WHAT...Widespread lows in the upper 20s, with temperatures falling to the low 20s in eastern Box Elder County, the western Uinta Basin, and Castle Country and mid to upper teens in the Sanpete and Sevier Valleys, west central and southwest Utah. * WHERE...Portions of central, northern, southern, and southwest Utah. * WHEN...For the first Freeze Warning, from 8 PM Thursday to noon MDT Friday. For the second Freeze Warning, from 8 PM Friday to noon MDT Saturday. * IMPACTS...Frost and freeze conditions could kill crops, other sensitive vegetation and damage unprotected outdoor plumbing.