A frigid Arctic air mass moved into Oregon December 5th and remained over the area through December 12th, when it finally abated as a Pacific system approached the area.

Extreme Cold/Wind Chill in MODOC COUNTY, CALIFORNIA
From 05-DEC-09 18:00:00 to 11-DEC-09 10:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Low temperatures in this zone during this interval were generally in the single digits above zero.  On the coldest nights...the 8th through the 10th, the coldest stations dipped below zero.  The coldest stations had lows ranging from 6 to 12 degrees below zero.  Temperatures warmed on the 11th but remained well below normal...and became more seasonable on the 12th.  Numerous broken pipes and other cold-related damage was reported during this interval.

Extreme Cold/Wind Chill in WESTERN SISKIYOU COUNTY, CALIFORNIA
From 05-DEC-09 18:00:00 to 11-DEC-09 10:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Low temperatures in this zone during this interval were generally in the teens.  On the coldest nights...the 9th and the 10th, the coldest stations dipped into the single digits.
Temperatures warmed on the 11th but remained well below normal...and became more seasonable on the 12th.  Numerous broken pipes and other cold-related damage was reported during this interval.

Extreme Cold/Wind Chill in SOUTH CENTRAL SISKIYOU COUNTY, CALIFORNIA
From 05-DEC-09 18:00:00 to 11-DEC-09 10:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Low temperatures in this zone during this interval were generally in the teens.  On the coldest nights...the 9th and the 10th, the coldest stations dipped into the single digits.
Temperatures warmed on the 11th but remained well below normal...and became more seasonable on the 12th.  Numerous broken pipes and other cold-related damage was reported during this interval.

Extreme Cold/Wind Chill in NORTH CENTRAL & SOUTHEAST SISKIYOU COUNTY, CALIFORNIA
From 05-DEC-09 18:00:00 to 11-DEC-09 10:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Low temperatures in this zone during this interval were generally in the single digits above zero.  On the coldest nights...the 8th through the 10th, the coldest stations dipped below zero.  The coldest stations had lows ranging from 6 to 11 degrees below zero.  Temperatures warmed on the 11th but remained well below normal...and became more seasonable on the 12th.  Numerous broken pipes and other cold-related damage was reported during this interval.

Extreme Cold/Wind Chill in NORTHEAST SISKIYOU AND NORTHWEST MODOC COUNTIES, CALIFORNIA
From 05-DEC-09 18:00:00 to 11-DEC-09 10:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Low temperatures in this zone during this interval were generally in the single digits above zero.  On the coldest nights...the 8th through the 10th, the coldest stations dipped below zero.  The coldest stations had lows ranging from 6 to 11 degrees below zero.  Temperatures warmed on the 11th but remained well below normal...and became more seasonable on the 12th.  Numerous broken pipes and other cold-related damage was reported during this interval.

Extreme Cold/Wind Chill in CENTRAL SISKIYOU COUNTY, CALIFORNIA
From 05-DEC-09 18:00:00 to 11-DEC-09 10:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Low temperatures in this zone during this interval were generally in the teens.  On the coldest nights...the 9th and the 10th, the coldest stations dipped into the single digits.
Temperatures warmed on the 11th but remained well below normal...and became more seasonable on the 12th.  Numerous broken pipes and other cold-related damage was reported during this interval.