Warm air from the Pacific Ocean was swept up the US and Canadian continental coasts this week. It hung over Alaska, causing unprecedented high temperatures - 67 degrees (19.4C) - which spun off torrential rain storms.
The storms dropped an inch of rain (25mm) in just a few hours. Then the temperature dropped back down, freezing everything in an event officials have called "Icemageddon".
"Ice is extremely difficult to remove once it has binded to the road surface. Even though air temps were warm ... roads were at sub-zero temps, which caused ice to bind to the surface," the department said in a tweet.
Another tweet issued by Alaska transportation officials called the winter storms "unprecedented."
In addition to shutting down roads, some regions reported power outages, forcing office closures.
The roof of the only grocery store in Delta Junction, about 95 miles east of Fairbanks, collapsed when nearly 10 inches of quickly falling snow built up over just a few hours.
The storms were so severe that the National Guard was activated to help rescue stranded individuals from the state's interior.
“The (State Emergency Operations Center) has been monitoring multiple weather-related incidents statewide this week,” Alaska National Guard Major General Torrence Saxe said in a statement. “For many communities throughout the Interior, reports indicate widespread power outages and significant disruptions for both road and air travel, and we are working with state and local agencies to assist as needed.”
The National Guard uses a tracked US Army Arctic vehicle to traverse the snow. It can take up to 15 people through the near-impassible snow dropped by particularly bad storms.
Climate Scientist Rick Thoman of the Alaska Centre for Climate Assessment and Police, spoke with the BBC about the weather event.
He told the outlet that global warming was driving the increasingly common weather anomalies.
"When all the pieces come together in a warming world we're going to get these unprecedented events, that's what we expect," he said.
Alaska was not the only state affected by the weather system.
Hundreds of flights were cancelled at Seattle’s Sea-Tac airport, and snow and rain caused flooding throughout parts of California, including Los Angeles.
Up to 16ft (5m) of snow has fallen in the state’s Sierra Nevada mountains, setting an all time high for snowfall.