* WHAT...Sub-freezing temperatures as low as 25 possible.

* WHERE...Antelope Valley.

* WHEN...From late Monday night through Tuesday morning.

* IMPACTS...Frost and freeze conditions could kill crops, other sensitive vegetation and possibly damage unprotected outdoor plumbing.

* WHAT...The South Coast AQMD has extended a mandatory wood-burning ban for residents in the South Coast Air Basin. The No-Burn rule bans burning wood, pellets, and manufactured fire logs in any indoor or outdoor wood-burning device.

* WHERE...The South Coast Air Basin, which includes Orange County and non-desert portions of Los Angeles, Riverside, and San Bernardino counties. No-Burn Day alerts do not apply to areas above 3,000 feet in elevation, the Coachella Valley, or the High Desert. Homes that rely on wood as a sole source of heat, low-income households and those without natural gas service also are exempt from the requirement.

* WHEN...until 11:59 PM Sunday.

* IMPACTS...Particles in smoke can get deep into the lungs and cause health problems (including asthma attacks), increases in emergency room visits, and hospitalizations. No-Burn Days are needed to protect public health when fine particle pollution levels are expected to be high anywhere in the South Coast Air Basin. No-Burn Days are based on fine particle pollution levels that are forecasted for an entire 24-hour period, which may not be reflected in real-time air quality maps.