Record-breaking temperatures and historic snowfalls are buffeting parts of the US, as states grapple with unusual winter weather and travellers' plans are thrust into chaos.
Alaska, which typically faces frigid temperatures and snowfall this year, has instead been hit with soaring temperatures and torrential rainfall.
Warm ocean waters north of Hawaii exacerbated a "heat dome" that delivered additional warmth to America's last frontier.
The island community of Kodiak set a new December high of 19C on Sunday afternoon, a state record, according to the Kodiak Tide Gauge Station. Kodiak Airport recorded a temperature of 18C, beating a previous December record set in 1984.
The soaring temperature also brought record rainfall in the state. Fairbanks experienced its wettest-ever day on record in December, with 23.6 centimetres of precipitation reported.
Meanwhile, after facing a historic summer drought earlier this year, parts of California are experiencing record-level snowfall.
The Central Sierra Snow Laboratory in northern California recorded nearly 5.2 metres of snow this month. Scientists say it is the snowiest December on record.
Snowfall is forecasted to continue in the Sierra Nevada mountains through Thursday, with additional rainfall and mountain snow expected to hit southern California.
The snowpack serves as a natural reservoir for California, and the Sierra snowpack accounts for 30 per cent of the state's fresh water supply for the year, according to the California Department of Water Resources. Last winter the Sierra snowpack was at an alarmingly low level and the reservoirs are still below the historical average, CNN reported.
With more snow expected, officials said this month's snowfall should help the parched reservoirs.
The snowfall and freezing temperatures have also disrupted travel. Interstate 80, buried by snow and beset by fallen trees, was shut down on Sunday from the Nevada state line to Placer County.
Travellers in Seattle, Washington, are still facing hundreds of airline cancellations because of excessive snowfall and cold. More than 1,000 flights into and out of Seattle-Tacoma Airport have been cancelled and hundreds more delayed since Sunday, the Seattle Times reported. On Tuesday, nearly one-quarter of all flights were cancelled.
Temperatures in normally mild Seattle have fallen well below freezing. The National Weather Service said the low for the city on Monday was -8.3C, breaking a record set in 1968.
City officials have opened severe weather shelters in response to the frigid temperatures and the mayor declared an emergency.
Warming shelters have also been opened in Oregon. The state on Tuesday issued a weather warning for several counties as temperatures were expected to dip below freezing.
December's unusual weather capped a year in which the US experienced a slew of extreme weather events, including the hottest summer on record, the largest wildfire in California's history and destructive hurricanes and tornadoes.