The significant cold snap that developed across interior Alaska on December 27th continued through January 12th. A cold upper level low across Siberia that moved into northern Alaska in late December was reinforced by another cold low that dropped south out of the high arctic and into interior Alaska on January 2nd.  The low dropped south to near Yakutat by January 4th, and kept the cold air locked in place across most of interior Alaska through January 11th.  The cold snap ended across most of the interior on the 11th, but lingered through the 12th on the Yukon Flats. Although the cold snap did not produce any record low temperatures, it was the most prolonged cold snap across interior Alaska since 1999.
In Fairbanks and North Pole the cold snap was accompanied by a prolonged period of ice fog that frequently reduced the visibility to one quarter mile or less.  There were 15 consecutive days where the low temperature was 40 below or colder at the Fairbanks International Airport, which was the most since 1973.  Only 1964 and 1971 have had more consecutive days with a low temperature of 40 below or colder.
The lowest temperature observed at the Fairbanks International Airport was 47 below, which was observed on January 6th and again on the 8th.  Many spots in the deeper valleys around Fairbanks had several nights with low temperatures between 50 and 55 below. The lowest official temperature that was observed during the cold snap was 68 below at Chicken.
Here are some notable temperatures that were observed through January 11th across interior Alaska:
Zone 216: Galena: 51 below, on the 2nd.
Zone 217: Ambler: 45 below, on the 3rd.
Zone 218: Arctic Village: 53 below, on the 9th.
Zone 219: Bettles: 51 below, on the 4th.
Zone 220:
Fort Yukon: 61 below, on the 4th.
Circle Hot Springs: 56 below, on the 5th.
Central: 55 below, on the 7th.
Zone 221: Nenana: 51 below, on the 4th.
Zone 222:
North Pole KJNP: 58 below, on the 4th.
Fairbanks International Airport: 47 below, on the 6th and 8th.
Zone 223: Delta Junction: 49 below, on the 5th and 6th.
Zone 224:
Chicken: 68 below, on the 8th.
O'Brien Creek: 65 below, on the 8th.
Northway: 61 below, on the 8th.
Tok: 60 below, on the 8th and 9th.
Eagle: 58 below, on the 8th.
Zone 225: Denali Park HQ: 41 below, on the 4th.
Zone 226:
Dry Creek: 57 below, on the 6th.
Chisana: 53 below, on the 7th.
The cold snap ended with a strong Chinook on January 15th through the 17th, and established many all-time record warm temperatures for the month of January across interior Alaska.  The high of 52 degrees at the Fairbanks International Airport was the warmest temperature ever observed during the months of January or February, and tied with December 4th and 7th of 1934 as the 3rd warmest temperature ever observed in Fairbanks during the three month period of December through February. The warmest temperature observed was 56 degrees at the Birch Lake RWIS.
Here are the new all-time January record highs as well as the previous records:
Zone 220:
Central: 48, previously 43 in 1963
Fort Yukon: 45, previously 40 in 1927
Zone 221:
Nenana: 54, previously 45 in 1991
Manley Hot Springs: 47, previously 46 in 1961
Zone 222:
Fairbanks International Airport: 52, previously 50 on January 15, 1981
University Experiment Station Cooperative Weather Station: 51; previously 47 on January 15, 1981
North Pole: 55, previously 50 on January 15, 1981
Eielson AFB: 52, previously 49 on January 15, 1981
UAF/College Observatory Cooperative Weather Station: 52; previously 47 on January 15, 1981
College 5NW Cooperative Weather Station: 51; previously 48 on January 15, 1981
Two Rivers Cooperative Weather Station: 58; previously 45 on January 15, 2001 (only 15 years of record)
Zone 223: Fort Greely/Delta Junction: 54, previously 52 on January 30, 2007.

Extreme Cold/Wind Chill in NE. SLOPES OF THE ERN AK RNG, ALASKA
From 01-JAN-09 00:00:00 to 11-JAN-09 12:00:00 (AKST-9)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Park/Forest Service

Extreme Cold/Wind Chill in LOWER KOYUKUK MIDDLE YKN VLYS, ALASKA
From 01-JAN-09 00:00:00 to 10-JAN-09 12:00:00 (AKST-9)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Extreme Cold/Wind Chill in UPPER KOBUK AND NOATAK VLYS, ALASKA
From 01-JAN-09 00:00:00 to 11-JAN-09 23:59:00 (AKST-9)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Extreme Cold/Wind Chill in S. SLOPES OF ERN BROOKS RANGE, ALASKA
From 01-JAN-09 00:00:00 to 11-JAN-09 23:59:00 (AKST-9)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Extreme Cold/Wind Chill in UPPER KOYUKUK VALLEY, ALASKA
From 01-JAN-09 00:00:00 to 11-JAN-09 14:00:00 (AKST-9)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Extreme Cold/Wind Chill in YUKON FLATS NEARBY UPLANDS, ALASKA
From 01-JAN-09 00:00:00 to 12-JAN-09 23:59:00 (AKST-9)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Extreme Cold/Wind Chill in WRN TANANA VLY WRN YUKON VLY, ALASKA
From 01-JAN-09 00:00:00 to 11-JAN-09 18:00:00 (AKST-9)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Extreme Cold/Wind Chill in MIDDLE TANANA VALLEY, ALASKA
From 01-JAN-09 00:00:00 to 11-JAN-09 23:59:00 (AKST-9)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Extreme Cold/Wind Chill in DELTANA AND TANANA, ALASKA
From 01-JAN-09 00:00:00 to 11-JAN-09 12:00:00 (AKST-9)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Extreme Cold/Wind Chill in UPR TANANA VLY FORTYMILE, ALASKA
From 01-JAN-09 00:00:00 to 11-JAN-09 23:59:00 (AKST-9)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Extreme Cold/Wind Chill in DENALI, ALASKA
From 01-JAN-09 00:00:00 to 11-JAN-09 12:00:00 (AKST-9)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Park/Forest Service