* WHAT...Widespread frost, but also sub-freezing temperatures as low as 29 degrees expected. * WHERE...In California, Modoc, Northeast Siskiyou and Northwest Modoc Counties, and South Central Siskiyou Counties. In Oregon, Central and Eastern Lake, Klamath Basin, and Northern and Eastern Klamath and Western Lake Counties. This includes Klamath Falls, Lakeview, Alturas, McCloud, Dorris, Tulelake, Chiloquin, and Sprague River. * WHEN...From 3 AM to 9 AM PDT Monday. * IMPACTS...Frost and freeze conditions could kill crops, other sensitive vegetation and possibly damage unprotected outdoor plumbing. * ADDITIONAL DETAILS...Freezing temperatures are also possible in much of the same area on Tuesday morning. The addition of some high clouds will be helpful, but dew points will be lower than on Monday morning.